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Clarify horizontal line test, RT-tracking overkill

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- round-trip-tracking is overkill for most use-cases
- clarify that horizontal line test is best used for landmarks and for
  multiple different grouping elements, rather than just any grouping
  element.
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Rohan Kumar 2022-05-18 18:31:55 -07:00
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@ -205,6 +205,8 @@ These metrics aren't useless, but they are incredibly naive: they only take into
### Round trips ### Round trips
Note: this section is overkill for most use-cases.
A supplementary metric to use alongside download size is round trips. Estimate the number of bytes and round-trips it takes to do the following: A supplementary metric to use alongside download size is round trips. Estimate the number of bytes and round-trips it takes to do the following:
1. Begin downloading the final blocking resource 1. Begin downloading the final blocking resource
@ -895,7 +897,7 @@ The remainder of the "Layout" section is possibly the most subjective part of th
A simple layout looks good at a variety of window sizes, rendering responsive layout changes unnecessary. Textual websites really don't need more than a single column; readers should be able to scan a page top-to-bottom, left-to-right (or right-to-left, depending on the locale) exactly once to read all its content. A simple layout looks good at a variety of window sizes, rendering responsive layout changes unnecessary. Textual websites really don't need more than a single column; readers should be able to scan a page top-to-bottom, left-to-right (or right-to-left, depending on the locale) exactly once to read all its content.
Verify this using the horizontal-line test: mentally draw a horizontal line across your page, and make sure it doesn't intersect more than one significant grouping element. The "source order viewer" in Chromium's DevTools can assist with this process. Verify this using the horizontal-line test: mentally draw a horizontal line across your page, and make sure it doesn't intersect more than one landmark. Ideally, it shouldn't intersect multiple different grouping elements either. The "source order viewer" in Chromium's DevTools can assist with this process.
=> https://html.spec.whatwg.org/dev/grouping-content.html#grouping-content "HTML living standard, section 4.4: Grouping content" lists grouping elements. => https://html.spec.whatwg.org/dev/grouping-content.html#grouping-content "HTML living standard, section 4.4: Grouping content" lists grouping elements.

86
content/posts/website-best-practices.md
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@ -235,6 +235,8 @@ Everything else is bullshit.
### Round trips ### Round trips
<p role="doc-tip">This sub-section is overkill for most use-cases.</p>
A supplementary metric to use alongside download size is round trips. Estimate the number of bytes and round-trips it takes to do the following: A supplementary metric to use alongside download size is round trips. Estimate the number of bytes and round-trips it takes to do the following:
1. Begin downloading the final blocking resource 1. Begin downloading the final blocking resource
@ -252,7 +254,7 @@ HTTP/3 uses QUIC instead of TCP, which makes things a bit different; the importa
### The golden kilobyte ### The golden kilobyte
Assume that your first impression must fit in the first kilobyte. Make good use of this golden kilobyte; most or all of it will likely be taken up by HTTP headers.[^6] Ideally, the first kilobyte transferred should inform the client of all blocking resources required, possibly using preload directives; all of these resources can then begin downloading over the same multiplexed HTTP/2 connection before the current round-trip finishes! Note that this works best if you took [my advice to avoid third-party content](#third-party-content). Assume that your first impression must fit in the first kilobyte.[^6] Make good use of this golden kilobyte; most or all of it will likely be taken up by HTTP headers.[^7] Ideally, the first kilobyte transferred should inform the client of all blocking resources required, possibly using preload directives; all of these resources can then begin downloading over the same multiplexed HTTP/2 connection before the current round-trip finishes! Note that this works best if you took [my advice to avoid third-party content](#third-party-content).
Apply these strategies in moderation. Including extra preload directives in your document markup might not help as much as you think, since their impact on page size could negate minor improvements. Micro-optimizations have diminishing returns; past a certain point, your effort is better spent elsewhere. Apply these strategies in moderation. Including extra preload directives in your document markup might not help as much as you think, since their impact on page size could negate minor improvements. Micro-optimizations have diminishing returns; past a certain point, your effort is better spent elsewhere.
@ -353,7 +355,7 @@ Pages should finish making all `GET` network requests while loading. This makes
One example is pagination. It's easier to download one long article ahead of time, but inconvenient to load each page separately. Displaying content all at once also improves searchability. The single-page approach has obvious limits: don't expect users to happily download a single-page novel. One example is pagination. It's easier to download one long article ahead of time, but inconvenient to load each page separately. Displaying content all at once also improves searchability. The single-page approach has obvious limits: don't expect users to happily download a single-page novel.
Another common offender is infinite-scrolling. In addition to requiring JavaScript, infinite-scrolling also makes it difficult for readers to find their old place upon re-visiting a page. This creates harsh consequences for accidental navigation. WordPress documentation lists [more problems with infinite scrolling](https://make.wordpress.org/accessibility/handbook/markup/infinite-scroll/).[^7] Another common offender is infinite-scrolling. In addition to requiring JavaScript, infinite-scrolling also makes it difficult for readers to find their old place upon re-visiting a page. This creates harsh consequences for accidental navigation. WordPress documentation lists [more problems with infinite scrolling](https://make.wordpress.org/accessibility/handbook/markup/infinite-scroll/).[^8]
A hybrid between the two is paginated content in which users click a "load next page" link to insert the next page at the end of the current page (typically using "dynamic content replacement"). It's essentially the same as infinite scrolling, except additional content is loaded after a click rather than by scrolling. This is only slightly less bad than infinite scrolling; it still has the same fundamental issue of allowing readers to lose their place. A hybrid between the two is paginated content in which users click a "load next page" link to insert the next page at the end of the current page (typically using "dynamic content replacement"). It's essentially the same as infinite scrolling, except additional content is loaded after a click rather than by scrolling. This is only slightly less bad than infinite scrolling; it still has the same fundamental issue of allowing readers to lose their place.
@ -442,7 +444,7 @@ Moreover, some search implemen&shy;tations (such as the one built into Firefox)
### Problem&shy;atic overrides {#problematic-overrides} ### Problem&shy;atic overrides {#problematic-overrides}
Search is so essential to some users' ability to navigate that some desktop users enable "type-ahead" search, to automatically begin a search upon typing multiple characters.[^8] If you ignored my advice to avoid JavaScript, at least think twice before using it to define custom keyboard shortcuts which interfere with this type of functionality. I singled out type-ahead search, but there are countless other examples of uncommon keyboard behavior that JavaScript overrides interfere with. Search is so essential to some users' ability to navigate that some desktop users enable "type-ahead" search, to automatically begin a search upon typing multiple characters.[^9] If you ignored my advice to avoid JavaScript, at least think twice before using it to define custom keyboard shortcuts which interfere with this type of functionality. I singled out type-ahead search, but there are countless other examples of uncommon keyboard behavior that JavaScript overrides interfere with.
Another problematic override is scroll-behavior. Enforcing smooth-scrolling (e.g., with the `scroll-behavior` CSS property) can interfere with the use of in-page search by slowing down jumps between matches. Rapidly darting around the page with smooth scrolling can cause motion sickness. Simply relying on users to override default behaviors violates the "inclusive by default" directive I encourage, since user preferences are fingerprintable and shift responsibility away from developers. Another problematic override is scroll-behavior. Enforcing smooth-scrolling (e.g., with the `scroll-behavior` CSS property) can interfere with the use of in-page search by slowing down jumps between matches. Rapidly darting around the page with smooth scrolling can cause motion sickness. Simply relying on users to override default behaviors violates the "inclusive by default" directive I encourage, since user preferences are fingerprintable and shift responsibility away from developers.
@ -475,7 +477,7 @@ Some people raised fingerprinting concerns when I suggested using the default "s
I don't know much about fingerprinting, except that you can't do font enumeration or accurately calculate font metrics without JavaScript. Since text-based websites that follow these best-practices don't send requests after the page loads and have no scripts, they shouldn't be able to fingerprint via font identification. I don't know much about fingerprinting, except that you can't do font enumeration or accurately calculate font metrics without JavaScript. Since text-based websites that follow these best-practices don't send requests after the page loads and have no scripts, they shouldn't be able to fingerprint via font identification.
Other websites can still fingerprint via font enumeration using JavaScript. They don't need to stop at seeing what sans-serif maps to: they can see available fonts on a user's system,[^9] the user's canvas fingerprint, window dimensions, etc. Some of these can be mitigated by [Firefox's protections against fingerprinting](https://support.mozilla.org/en-US/kb/firefox-protection-against-fingerprinting), but these protections understandably override user font preferences. Other websites can still fingerprint via font enumeration using JavaScript. They don't need to stop at seeing what sans-serif maps to: they can see available fonts on a user's system,[^10] the user's canvas fingerprint, window dimensions, etc. Some of these can be mitigated by [Firefox's protections against fingerprinting](https://support.mozilla.org/en-US/kb/firefox-protection-against-fingerprinting), but these protections understandably override user font preferences.
Ultimately, surveillance self-defense on the web is an arms race full of trade-offs. If you want both privacy and customizability, the web is not the place to look; try Gemini or Gopher instead. Ultimately, surveillance self-defense on the web is an arms race full of trade-offs. If you want both privacy and customizability, the web is not the place to look; try Gemini or Gopher instead.
@ -483,7 +485,7 @@ Ultimately, surveillance self-defense on the web is an arms race full of trade-o
Browsers allow users to zoom by adjusting size metrics. Additionally, most browsers allow users to specify a minimum font size. Minimum sizes don't always work; setting size values in `px` can override these settings. Browsers allow users to zoom by adjusting size metrics. Additionally, most browsers allow users to specify a minimum font size. Minimum sizes don't always work; setting size values in `px` can override these settings.
In your stylesheets, avoid using `px` where possible. Define sizes and dimensions using relative units (preferably `em`). Exceptions exist for some decorations (e.g. borders),[^10] but they are uncommon. In your stylesheets, avoid using `px` where possible. Define sizes and dimensions using relative units (preferably `em`). Exceptions exist for some decorations (e.g. borders),[^11] but they are uncommon.
{{<codefigure>}} {{< codecaption lang="CSS" >}} {{<codefigure>}} {{< codecaption lang="CSS" >}}
@ -503,14 +505,14 @@ Beyond alt-text
Expect some readers to have images disabled or unloaded. Examples include: Expect some readers to have images disabled or unloaded. Examples include:
* Blind readers * Blind readers
* Users with metered connections: sometimes they disable all images, and other times they only disable images surpassing a size threshold[^11] * Users with metered connections: sometimes they disable all images, and other times they only disable images surpassing a size threshold[^12]
* People experiencing packet loss who fail to download some images * People experiencing packet loss who fail to download some images
* Users of textual browsers * Users of textual browsers
Accordingly, follow good practices for alt-text: Accordingly, follow good practices for alt-text:
* Concisely summarize the image content the best you can, without repeating the surrounding content. * Concisely summarize the image content the best you can, without repeating the surrounding content.
* Images should usually have alt-text under 100 char&shy;acters, excluding punctuation.[^12] Save longer descriptions for a caption or <code>aria-<wbr>des&shy;cribedby</code>. Exceptions exist. * Images should usually have alt-text under 100 char&shy;acters, excluding punctuation.[^13] Save longer descriptions for a caption or <code>aria-<wbr>des&shy;cribedby</code>. Exceptions exist.
* Don't include significant information that isn't present in the image; I'll cover how to handle supple&shy;mentary information in the next subsections. * Don't include significant information that isn't present in the image; I'll cover how to handle supple&shy;mentary information in the next subsections.
The <abbr title="Web Accessibility Initiative">WAI</abbr> provides some guidelines in <cite>[An `alt` Decision Tree](https://www.w3.org/WAI/tutorials/images/decision-tree/)</cite>. It's a little lacking in nuance, but makes for a good starting point. Remember that guidelines and "good practices" always have exceptions. The <abbr title="Web Accessibility Initiative">WAI</abbr> provides some guidelines in <cite>[An `alt` Decision Tree](https://www.w3.org/WAI/tutorials/images/decision-tree/)</cite>. It's a little lacking in nuance, but makes for a good starting point. Remember that guidelines and "good practices" always have exceptions.
@ -585,7 +587,7 @@ A <dfn>`longdesc`</dfn> attribute used to be another way to reference an image t
The recommended way to link to a transcript is by hyperlinking the image (i.e., wrapping it with `<a>`) or semantically grouping the image with its transcript. Put a short summary in the alt-text, and mention the availability of a transcript in a visible caption. The recommended way to link to a transcript is by hyperlinking the image (i.e., wrapping it with `<a>`) or semantically grouping the image with its transcript. Put a short summary in the alt-text, and mention the availability of a transcript in a visible caption.
A [StackOverflow thread about comic transcripts](https://stackoverflow.com/questions/65564539/what-is-the-semantically-correct-way-to-include-transcript-from-a-comic) outlines a good approach to semantically grouping images and transcripts, and my approach is similar. I group an image, alt-text, and caption in a `<figure>` element and follow it with a transcript in a `<details>` element. I use <code>aria-<wbr>des&shy;cribedby</code> to semantically link the figure and the transcript.[^13] A [StackOverflow thread about comic transcripts](https://stackoverflow.com/questions/65564539/what-is-the-semantically-correct-way-to-include-transcript-from-a-comic) outlines a good approach to semantically grouping images and transcripts, and my approach is similar. I group an image, alt-text, and caption in a `<figure>` element and follow it with a transcript in a `<details>` element. I use <code>aria-<wbr>des&shy;cribedby</code> to semantically link the figure and the transcript.[^14]
An image, alt-text, figure caption, and transcript combine to form a complex relationship that should be grouped together in a single landmark. I put all three inside a `<section>` with a heading, and give the group an `aria-label` that indicates the presence of the three sub-elements. Using a `section` landmark ensures that the figure and caption remain together as a single unit. The [html code](#xkcd-html) for the [xkcd comic earlier in the page](#infinite-scrolling) is a representative example. An image, alt-text, figure caption, and transcript combine to form a complex relationship that should be grouped together in a single landmark. I put all three inside a `<section>` with a heading, and give the group an `aria-label` that indicates the presence of the three sub-elements. Using a `section` landmark ensures that the figure and caption remain together as a single unit. The [html code](#xkcd-html) for the [xkcd comic earlier in the page](#infinite-scrolling) is a representative example.
@ -669,7 +671,7 @@ Even if you set custom colors, ensure that the page is compatible with color ove
[This page's canonical location](https://seirdy.one/2020/11/23/website-best-practices.html) is an example application of Technique C25 (and the related [Technique G148](https://www.w3.org/WAI/WCAG22/Techniques/general/G148)). It only uses non-default colors when a user agent requests a dark color scheme (using the `prefers-color-scheme` CSS media query; see the next subsection) and for lightening borders. Any image with a solid background may match the page background; to ensure that their dimensions are clear, I surrounded them with borders. Most browsers will render these borders with the default foreground color, which should be visually distinct from the background. I included borders and/or horizontal rules to break up some sections, since heading-based delineation is either unavailable or insufficient for them. When overriding color schemes, the page layout remains clear. [This page's canonical location](https://seirdy.one/2020/11/23/website-best-practices.html) is an example application of Technique C25 (and the related [Technique G148](https://www.w3.org/WAI/WCAG22/Techniques/general/G148)). It only uses non-default colors when a user agent requests a dark color scheme (using the `prefers-color-scheme` CSS media query; see the next subsection) and for lightening borders. Any image with a solid background may match the page background; to ensure that their dimensions are clear, I surrounded them with borders. Most browsers will render these borders with the default foreground color, which should be visually distinct from the background. I included borders and/or horizontal rules to break up some sections, since heading-based delineation is either unavailable or insufficient for them. When overriding color schemes, the page layout remains clear.
Color overrides go well beyond simple foreground and background color changes. Windows High Contrast Mode (<abbr title="Windows High Contrast Mode">WHCM</abbr>) is perhaps the best example. [WHCM makes advanced modifications to color palettes](#win-hcm): it colors elements with a user-specified palette, all according to semantic markup while ignoring ARIA overrides.[^14] Color overrides go well beyond simple foreground and background color changes. Windows High Contrast Mode (<abbr title="Windows High Contrast Mode">WHCM</abbr>) is perhaps the best example. [WHCM makes advanced modifications to color palettes](#win-hcm): it colors elements with a user-specified palette, all according to semantic markup while ignoring ARIA overrides.[^15]
<abbr title="Windows High Contrast Mode">WHCM</abbr> leads the standardization process for the `forced-colors` CSS media feature, but it isn't the only implementation of the underlying idea. If you navigate to <samp>about:preferences</samp> in Firefox and activate the <samp translate="yes">Colors</samp> button in the "Language and Appearance" section, you'll be presented with the option to override website palettes with [your own default colors](#default-colors). <abbr title="Windows High Contrast Mode">WHCM</abbr> leads the standardization process for the `forced-colors` CSS media feature, but it isn't the only implementation of the underlying idea. If you navigate to <samp>about:preferences</samp> in Firefox and activate the <samp translate="yes">Colors</samp> button in the "Language and Appearance" section, you'll be presented with the option to override website palettes with [your own default colors](#default-colors).
@ -747,14 +749,14 @@ Accounting for halation, overstimulation, and high-contrast needs is hard to do
Color palettes need to be effective for different types of vision deficiencies (e.g. color blindnesses) and screens. Color blindness is a far more nuanced topic than "the inability to see some colors". <span itemprop="citation" itemscope itemtype="https://schema.org/BlogPosting">{{<indieweb-person itemprop="author" first-name="Rob" last-name="Pike" url="http://herpolhode.com/rob/">}} describes his experience in {{<cited-work name="Color blindness" extraName="headline" url="https://commandcenter.blogspot.com/2020/09/color-blindness-is-inaccurate-term.html">}}</span>. Color blindness manifests in complex ways. Testing in grayscale is a great start, but it doesn't account for all kinds of color vision deficiencies. Color palettes need to be effective for different types of vision deficiencies (e.g. color blindnesses) and screens. Color blindness is a far more nuanced topic than "the inability to see some colors". <span itemprop="citation" itemscope itemtype="https://schema.org/BlogPosting">{{<indieweb-person itemprop="author" first-name="Rob" last-name="Pike" url="http://herpolhode.com/rob/">}} describes his experience in {{<cited-work name="Color blindness" extraName="headline" url="https://commandcenter.blogspot.com/2020/09/color-blindness-is-inaccurate-term.html">}}</span>. Color blindness manifests in complex ways. Testing in grayscale is a great start, but it doesn't account for all kinds of color vision deficiencies.
Different screens and display-calibrations render color differently; what may look like a light-gray on a cheap monitor could look nearly black on a high-end OLED screen. Try to test on both high- and low-end displays, especially when designing a dark color scheme.[^15] Different screens and display-calibrations render color differently; what may look like a light-gray on a cheap monitor could look nearly black on a high-end OLED screen. Try to test on both high- and low-end displays, especially when designing a dark color scheme.[^16]
Color schemes should also look good to users who apply gamma adjustments. Most operating systems and desktop environments bundle a feature to reduce the screen color temperature at night, while some individuals may select a higher one in the morning. Color schemes should also look good to users who apply gamma adjustments. Most operating systems and desktop environments bundle a feature to reduce the screen color temperature at night, while some individuals may select a higher one in the morning.
In defense of link under&shy;lines {#in-defense-of-link-underlines} In defense of link under&shy;lines {#in-defense-of-link-underlines}
---------------------------------- ----------------------------------
Some typographers insist that [underlined on-screen text is obsolete](https://practicaltypography.com/underlining.html),[^16] and that hyperlinks are no exception. I disagree. Some typographers insist that [underlined on-screen text is obsolete](https://practicaltypography.com/underlining.html),[^17] and that hyperlinks are no exception. I disagree.
Readers already expect underlined text to signify a hyperlink. Don't break fundamental affordances for aesthetics. Underlines are also necessary to distinguish the beginnings and ends of multiple consecutive links, especially among color-blind users. Readers already expect underlined text to signify a hyperlink. Don't break fundamental affordances for aesthetics. Underlines are also necessary to distinguish the beginnings and ends of multiple consecutive links, especially among color-blind users.
@ -799,7 +801,7 @@ Some image optimization tools I use:
: The reference WebP encoder; has dedicated lossless and lossy modes. Lossy WebP compression isn't always better than JPEG, but lossless WebP consistently beats PNG. : The reference WebP encoder; has dedicated lossless and lossy modes. Lossy WebP compression isn't always better than JPEG, but lossless WebP consistently beats PNG.
`avifenc` `avifenc`
: The reference AVIF encoder, included in [libavif](https://github.com/AOMediaCodec/libavif).[^17] AVIF lossless compression is typically useless, but its lossy compression is pretty unique in that it leans towards detail removal rather than introducing compression artifacts. Note that AVIF is not supported by Safari or most WebKit-based browsers. : The reference AVIF encoder, included in [libavif](https://github.com/AOMediaCodec/libavif).[^18] AVIF lossless compression is typically useless, but its lossy compression is pretty unique in that it leans towards detail removal rather than introducing compression artifacts. Note that AVIF is not supported by Safari or most WebKit-based browsers.
I put together [a quick script](https://git.sr.ht/~seirdy/dotfiles/tree/3b722a843f3945a1bdf98672e09786f0213ec6f6/Executables/shell-scripts/bin/optimize-image) to losslessly optimize images using these programs. For lossy compression, I typically use [GNU Parallel](https://www.gnu.org/software/parallel/) to mass-generate images using different options before selecting the smallest image at the minimum acceptable quality. Users who'd rather avoid the command line while performing lossy compression can instead check out [Squoosh](https://squoosh.app/), a JavaScript app that bundles Web&shy;Assembly-compiled encoders; I've heard good things about it. I put together [a quick script](https://git.sr.ht/~seirdy/dotfiles/tree/3b722a843f3945a1bdf98672e09786f0213ec6f6/Executables/shell-scripts/bin/optimize-image) to losslessly optimize images using these programs. For lossy compression, I typically use [GNU Parallel](https://www.gnu.org/software/parallel/) to mass-generate images using different options before selecting the smallest image at the minimum acceptable quality. Users who'd rather avoid the command line while performing lossy compression can instead check out [Squoosh](https://squoosh.app/), a JavaScript app that bundles Web&shy;Assembly-compiled encoders; I've heard good things about it.
@ -920,7 +922,7 @@ Users of <abbr title="assistive technology">AT</abbr>s such as screen readers pr
Try using a tool to view a list of all your link names. Just about every screen reader and some browser extensions should offer this functionality. Minimize links with ambiguous names, and ensure that identical link names have identical destinations. Try using a tool to view a list of all your link names. Just about every screen reader and some browser extensions should offer this functionality. Minimize links with ambiguous names, and ensure that identical link names have identical destinations.
Think twice before placing important content immediately after skippable content such as nested landmarks, long code snippets, figures, and large lists. AT users who wish to skip content may jump directly to the next heading, glossing over anything between the skippable content and subsequent heading; this is especially common on mobile devices.[^18] When it makes sense to do so, place skippable content in its own sections and/or at the end of its parent section. Think twice before placing important content immediately after skippable content such as nested landmarks, long code snippets, figures, and large lists. AT users who wish to skip content may jump directly to the next heading, glossing over anything between the skippable content and subsequent heading; this is especially common on mobile devices.[^19] When it makes sense to do so, place skippable content in its own sections and/or at the end of its parent section.
### Arbitrary viewports ### Arbitrary viewports
@ -928,7 +930,7 @@ The remainder of the "Layout" section is possibly the most subjective part of th
A simple layout looks good at a variety of window sizes, rendering responsive layout changes unnecessary. Textual websites really don't need more than a single column; readers should be able to scan a page top-to-bottom, left-to-right (or right-to-left, depending on the locale) exactly once to read all its content. A simple layout looks good at a variety of window sizes, rendering responsive layout changes unnecessary. Textual websites really don't need more than a single column; readers should be able to scan a page top-to-bottom, left-to-right (or right-to-left, depending on the locale) exactly once to read all its content.
Verify this using the horizontal-line test: mentally draw a horizontal line across your page, and make sure it doesn't intersect more than one significant [grouping element](https://html.spec.whatwg.org/dev/grouping-content.html). The "source order viewer" in Chromium's DevTools can assist with this process. Verify this using the horizontal-line test: mentally draw a horizontal line across your page, and make sure it doesn't intersect more than one landmark. Ideally it shouldn't intersect multiple different [grouping elements](https://html.spec.whatwg.org/dev/grouping-content.html) either. The "source order viewer" in Chromium's DevTools can assist with this process.
Keeping a single-column layout that doesn't require responsive layout changes ensures smooth window re-sizing. Doing so while keeping an identical source, DOM, and visual order ensures layout consistency: spatial references such as "the paragraph above this heading" or "the bottom image of a section" will be unambiguous to screen reader, phone, and desktop users. Achieving this type of layout entails using the WCAG&nbsp;2.2 techniques <cite>[C27: Making the DOM order match the visual order](https://www.w3.org/WAI/WCAG22/Techniques/css/C27.html)</cite> as well as <cite>[C6: Positioning content based on structural markup](https://www.w3.org/WAI/WCAG22/Techniques/css/C6)</cite>. Keeping a single-column layout that doesn't require responsive layout changes ensures smooth window re-sizing. Doing so while keeping an identical source, DOM, and visual order ensures layout consistency: spatial references such as "the paragraph above this heading" or "the bottom image of a section" will be unambiguous to screen reader, phone, and desktop users. Achieving this type of layout entails using the WCAG&nbsp;2.2 techniques <cite>[C27: Making the DOM order match the visual order](https://www.w3.org/WAI/WCAG22/Techniques/css/C27.html)</cite> as well as <cite>[C6: Positioning content based on structural markup](https://www.w3.org/WAI/WCAG22/Techniques/css/C6)</cite>.
@ -1008,7 +1010,7 @@ Where long inline `<code>` elements can trigger horizontal scrolling, consider a
### Keeping text together ### Keeping text together
Soft hyphens are great for splitting up text, but some text should stay together. The phrase "10&nbsp;cm", for instance, would flow poorly if "10" and "cm" appeared on separate lines. Splitting text becomes especially painful on narrow viewports. A non-breaking space keeps the surrounding text from being re-flowed. Use the `&nbsp;` HTML entity instead of a space: `10&nbsp;cm`. <span itemprop="mentions" itemscope itemtype="https://schema.org/Book">{{<cited-work name="Practical Typography" url="https://practicaltypography.com/">}} by {{<indieweb-person first-name="Matthew" last-name="Butterick" url="https://mbtype.com/bio.html">}},[^16] a typographer,</span> describes [where to use the non-breaking space](https://briefs.video/videos/is-progressive-enhancement-dead-yet/) in more detail. Soft hyphens are great for splitting up text, but some text should stay together. The phrase "10&nbsp;cm", for instance, would flow poorly if "10" and "cm" appeared on separate lines. Splitting text becomes especially painful on narrow viewports. A non-breaking space keeps the surrounding text from being re-flowed. Use the `&nbsp;` HTML entity instead of a space: `10&nbsp;cm`. <span itemprop="mentions" itemscope itemtype="https://schema.org/Book">{{<cited-work name="Practical Typography" url="https://practicaltypography.com/">}} by {{<indieweb-person first-name="Matthew" last-name="Butterick" url="https://mbtype.com/bio.html">}},[^17] a typographer,</span> describes [where to use the non-breaking space](https://briefs.video/videos/is-progressive-enhancement-dead-yet/) in more detail.
One exception to the rules from <cite>Practical Typography</cite>: don't use a non-breaking space if it would trigger two-dimensional scrolling on a narrow viewport. Between broken text and two-dimensional scrolling, broken text is the lesser evil. I personally set a cutoff at 2.5&nbsp;cm (1&nbsp;inch) at 125% zoom. One exception to the rules from <cite>Practical Typography</cite>: don't use a non-breaking space if it would trigger two-dimensional scrolling on a narrow viewport. Between broken text and two-dimensional scrolling, broken text is the lesser evil. I personally set a cutoff at 2.5&nbsp;cm (1&nbsp;inch) at 125% zoom.
@ -1234,7 +1236,7 @@ On one hand, users who need enhanced focus visibility may override the default f
The WCAG [Success Criterion 2.4.12](https://w3c.github.io/wcag/guidelines/22/#focus-appearance-enhanced) recommends making focus indicators 2&nbsp;px thick. While this success criterion is only AAA-level, it's easy enough to meet and beneficial enough to others that we should all meet it. The WCAG [Success Criterion 2.4.12](https://w3c.github.io/wcag/guidelines/22/#focus-appearance-enhanced) recommends making focus indicators 2&nbsp;px thick. While this success criterion is only AAA-level, it's easy enough to meet and beneficial enough to others that we should all meet it.
You can use `:focus` and `:focus-visible` to highlight selected and keyboard-focused elements, respectively. Take care to only alter styling, not behavior: only keyboard-focusable elements should receive outlines. Modern browser stylesheets use `:focus-visible` instead of `:focus`; old browsers only support `:focus` and re-style a subset of focusable elements. Your stylesheets should do the same, to match browser behavior.[^19] You can use `:focus` and `:focus-visible` to highlight selected and keyboard-focused elements, respectively. Take care to only alter styling, not behavior: only keyboard-focusable elements should receive outlines. Modern browser stylesheets use `:focus-visible` instead of `:focus`; old browsers only support `:focus` and re-style a subset of focusable elements. Your stylesheets should do the same, to match browser behavior.[^20]
{{<codefigure>}} {{<codefigure>}}
@ -1312,7 +1314,7 @@ Screen readers on touch screen devices are also quite different from their deskt
Screen reader implemen&shy;tations often skip punctuation marks like the exclamation point ("!"). Ensure that meaning doesn't rely too heavily on such punctuation. Screen reader implemen&shy;tations often skip punctuation marks like the exclamation point ("!"). Ensure that meaning doesn't rely too heavily on such punctuation.
Screen readers have varying levels of verbosity. The default verbosity level doesn't always convey inline emphasis, such as `<em>`, `<code>`, or `<strong>`. Ensure that your meaning carries through without these semantics.[^20] Screen readers have varying levels of verbosity. The default verbosity level doesn't always convey inline emphasis, such as `<em>`, `<code>`, or `<strong>`. Ensure that your meaning carries through without these semantics.[^21]
Default verbosity does, however, convey symbols and emoji. Use symbols and emoji judiciously, since they can get pretty noisy if you aren't careful. Use `aria-labelledby` on symbols when appropriate; I used labels to mark my footnote backlinks, which would otherwise be read as <samp>right arrow curving left</samp>. If you have to use a symbol or emoji, first test how assistive technologies announce it; the emoji name may not communicate what you expect. Default verbosity does, however, convey symbols and emoji. Use symbols and emoji judiciously, since they can get pretty noisy if you aren't careful. Use `aria-labelledby` on symbols when appropriate; I used labels to mark my footnote backlinks, which would otherwise be read as <samp>right arrow curving left</samp>. If you have to use a symbol or emoji, first test how assistive technologies announce it; the emoji name may not communicate what you expect.
@ -1341,7 +1343,7 @@ No matter how simple a page is, I don't think simplicity eliminates the need for
Automated tests--especially accessibility tests--are a supplement to manual tests, not a replacement for them. Think of them as time-savers that bring up issues for further research, containing both false positives and false negatives. Automated tests--especially accessibility tests--are a supplement to manual tests, not a replacement for them. Think of them as time-savers that bring up issues for further research, containing both false positives and false negatives.
These are the tools I use regularly. I've deliberately excluded tools that would be redundant.[^21] These are the tools I use regularly. I've deliberately excluded tools that would be redundant.[^22]
1. [Nu HTML checker](https://validator.nu/): The W3C's official HTML validator. Valid HTML ensures broader compatibility with a wider range of agents. Note that it uses Jigsaw under the hood for CSS validation, which hasn't implemented support for certain CSS features I've reco&shy;mmended elsewhere on this page. Watch out for false positives. 1. [Nu HTML checker](https://validator.nu/): The W3C's official HTML validator. Valid HTML ensures broader compatibility with a wider range of agents. Note that it uses Jigsaw under the hood for CSS validation, which hasn't implemented support for certain CSS features I've reco&shy;mmended elsewhere on this page. Watch out for false positives.
@ -1349,7 +1351,7 @@ These are the tools I use regularly. I've deliberately excluded tools that would
3. [Light&shy;house](https://developers.google.com/web/tools/lighthouse/): An auditing tool by Google that uses the DevTools protocol in any Chromium-based browser. Skip the "Access&shy;ibility" category, since it just runs a subset of axe-core's audits. The most useful audit is the tap target size check in its "SEO" category. Note that your `sandbox` CSP directive will need to include `allow-scripts` for it to function. 3. [Light&shy;house](https://developers.google.com/web/tools/lighthouse/): An auditing tool by Google that uses the DevTools protocol in any Chromium-based browser. Skip the "Access&shy;ibility" category, since it just runs a subset of axe-core's audits. The most useful audit is the tap target size check in its "SEO" category. Note that your `sandbox` CSP directive will need to include `allow-scripts` for it to function.
4. [Webhint](https://webhint.io/): Similar to Light&shy;house. Again, you can ignore the accessibility audits if you already use axe-core. I personally disagree with some of its hints: the "unneeded HTTP headers" hint ignores the fact that the CSP can have an effect on non-hypertext assets, the "HTTP cache" hint has an unreasonable bias against caching HTML, and the "Correct `Content-Type` header" recommends charset attributes a bit too agg&shy;ressively[^22]. 4. [Webhint](https://webhint.io/): Similar to Light&shy;house. Again, you can ignore the accessibility audits if you already use axe-core. I personally disagree with some of its hints: the "unneeded HTTP headers" hint ignores the fact that the CSP can have an effect on non-hypertext assets, the "HTTP cache" hint has an unreasonable bias against caching HTML, and the "Correct `Content-Type` header" recommends charset attributes a bit too agg&shy;ressively[^23].
5. [IBM Equal Access Access&shy;ibility Checker](https://www.ibm.com/able/toolkit/verify/automated/): Has a scope similar to axe-core. Its "Sensory Characteristics" audit seems unique. 5. [IBM Equal Access Access&shy;ibility Checker](https://www.ibm.com/able/toolkit/verify/automated/): Has a scope similar to axe-core. Its "Sensory Characteristics" audit seems unique.
@ -1373,7 +1375,7 @@ These tests begin reasonably, but gradually grow absurd. Once again, use your ju
1. Test in all three major browser engines: Blink, Gecko, and WebKit. 1. Test in all three major browser engines: Blink, Gecko, and WebKit.
2. Evaluate the heaviness and complexity of your scripts (if any) by testing with your browser's <abbr title="just-in-time">JIT</abbr> compilation disabled.[^23] 2. Evaluate the heaviness and complexity of your scripts (if any) by testing with your browser's <abbr title="just-in-time">JIT</abbr> compilation disabled.[^24]
3. Test using the Tor Browser's safest security level enabled (disables JS and other features). 3. Test using the Tor Browser's safest security level enabled (disables JS and other features).
@ -1399,7 +1401,7 @@ These tests begin reasonably, but gradually grow absurd. Once again, use your ju
14. Try printing out your page in black-and-white from an unorthodox graphical browser. 14. Try printing out your page in black-and-white from an unorthodox graphical browser.
15. Download your webpage and test how multiple word processors render and generate PDFs from it.[^24] 15. Download your webpage and test how multiple word processors render and generate PDFs from it.[^25]
16. Combine conversion tools. Combine an HTML-<wbr>to-<wbr>EPUB converter and an EPUB-<wbr>to-<wbr>PDF converter, or stack multiple article-extraction utilities. Be creative and enjoy breaking your site. When something breaks, examine the breakage and see if it's caused by an issue in your markup, or a CSS feature with an equivalent alternative. 16. Combine conversion tools. Combine an HTML-<wbr>to-<wbr>EPUB converter and an EPUB-<wbr>to-<wbr>PDF converter, or stack multiple article-extraction utilities. Be creative and enjoy breaking your site. When something breaks, examine the breakage and see if it's caused by an issue in your markup, or a CSS feature with an equivalent alternative.
@ -1533,7 +1535,7 @@ One resource I found useful (that eventually featured this article!) was the "Yo
If you've got some time on your hands, I _highly_ recommend reading the <cite>[Web Content Accessibility Guidelines (WCAG)&nbsp;2.2](https://www.w3.org/TR/WCAG22/)</cite>. The WCAG 2 standard is technology-neutral, so it doesn't contain Web-specific advice. For that, check the <cite>[How to Meet WCAG (Quick Reference)](https://www.w3.org/WAI/WCAG22/quickref)</cite>. It combines the WCAG with its supplementary [list of techniques](https://www.w3.org/WAI/WCAG22/Techniques/). If you've got some time on your hands, I _highly_ recommend reading the <cite>[Web Content Accessibility Guidelines (WCAG)&nbsp;2.2](https://www.w3.org/TR/WCAG22/)</cite>. The WCAG 2 standard is technology-neutral, so it doesn't contain Web-specific advice. For that, check the <cite>[How to Meet WCAG (Quick Reference)](https://www.w3.org/WAI/WCAG22/quickref)</cite>. It combines the WCAG with its supplementary [list of techniques](https://www.w3.org/WAI/WCAG22/Techniques/).
The WCAG are an excellent starting point for learning about accessibility, but make for a poor stopping point. Much of the content on this page simply isn't covered by the WCAG. One of my favorite resources for learning about what the WCAG _doesn't_ cover is [Axess Lab](https://axesslab.com/articles/). The WCAG are an excellent starting point for learning about accessibility, but make for a poor stopping point. Much of the content on this page simply isn't covered by the WCAG. One of my favorite resources for learning about what the WCAG _doesn't_ cover is [Axess Lab's articles](https://axesslab.com/articles/).
I've learned about a great number of under&shy;represented ways to browse from the Fediverse, particularly from [this subthread asking people to share](https://pleroma.envs.net/notice/AHqp3TEDFoyz0W4nbc) (requires JavaScript; [plaintext mirror](https://gopher.envs.net/pleroma.envs.net:7070/1/notices/AHqp3TEDFoyz0W4nbc)). Several responses informed updates to this page. I've learned about a great number of under&shy;represented ways to browse from the Fediverse, particularly from [this subthread asking people to share](https://pleroma.envs.net/notice/AHqp3TEDFoyz0W4nbc) (requires JavaScript; [plaintext mirror](https://gopher.envs.net/pleroma.envs.net:7070/1/notices/AHqp3TEDFoyz0W4nbc)). Several responses informed updates to this page.
@ -1554,47 +1556,49 @@ A special thanks goes out to GothAlice for the questions she answered in <samp>#
[^5]: <span itemprop="citation" itemscope itemtype="https://schema.org/TechArticle">{{<cited-work name="High-Performance Browser Networking" url="https://hpbn.co/building-blocks-of-tcp/" extraName="headline">}} by {{<indieweb-person first-name="Ilya" last-name="Grigorik" url="https://www.igvita.com/" itemprop="author">}}</span> gives a great introduction to how TCP works, if you'd like more details. [^5]: <span itemprop="citation" itemscope itemtype="https://schema.org/TechArticle">{{<cited-work name="High-Performance Browser Networking" url="https://hpbn.co/building-blocks-of-tcp/" extraName="headline">}} by {{<indieweb-person first-name="Ilya" last-name="Grigorik" url="https://www.igvita.com/" itemprop="author">}}</span> gives a great introduction to how TCP works, if you'd like more details.
[^6]: HPACK and QPACK header compression includes dictionaries containing common header names, and some common header values; HPACK lists them in "Appendix A" of <span itemprop="citation" itemscope itemtype="https://schema.org/TechArticle">{{<cited-work name="RFC 7541" extraName="headline" url="https://datatracker.ietf.org/doc/html/rfc7541#appendix-A">}}</span>. If a header name or name-value pair one of these predefined table entries, its effective size can be reduced to a single byte. If a header has a value that isn't covered by the table, consider minifying it by removing unnecessary whitespace. [^6]: This one-kilobyte limit is a semi-arbitrary rule-of-thumb I came up with. It's a simple number easier to work with than the number of bytes left in the earliest contentful round-trip, yet it typically falls within that quota.
[^7]: HPACK and QPACK header compression includes dictionaries containing common header names, and some common header values; HPACK lists them in "Appendix A" of <span itemprop="citation" itemscope itemtype="https://schema.org/TechArticle">{{<cited-work name="RFC 7541" extraName="headline" url="https://datatracker.ietf.org/doc/html/rfc7541#appendix-A">}}</span>. If a header name or name-value pair one of these predefined table entries, its effective size can be reduced to a single byte. If a header has a value that isn't covered by the table, consider minifying it by removing unnecessary whitespace.
Remember that if your golden first kilobyte already lists all essential resources, these could be considered premature optimi&shy;zations. Real bottlenecks lie elsewhere. Remember that if your golden first kilobyte already lists all essential resources, these could be considered premature optimi&shy;zations. Real bottlenecks lie elsewhere.
[^7]: Ironically, that page doesn't load the main text without JavaScript despite citing a JavaScript requirement as a downside. If you can't load the page, the same issues with infinte scroll are outlined in the "Accessibility concerns for infinite scroll" section of <span itemprop="citation" itemscope itemtype="https://schema.org/BlogPosting">{{<cited-work url="https://addyosmani.com/blog/infinite-scroll-without-layout-shifts/" name="Infinite Scroll without Layout Shifts" extraName="headline">}} by {{<indieweb-person itemprop="author" first-name="Addy" last-name="Osmani" url="https://addyosmani.com/">}}</span>. [^8]: Ironically, that page doesn't load the main text without JavaScript despite citing a JavaScript requirement as a downside. If you can't load the page, the same issues with infinte scroll are outlined in the "Accessibility concerns for infinite scroll" section of <span itemprop="citation" itemscope itemtype="https://schema.org/BlogPosting">{{<cited-work url="https://addyosmani.com/blog/infinite-scroll-without-layout-shifts/" name="Infinite Scroll without Layout Shifts" extraName="headline">}} by {{<indieweb-person itemprop="author" first-name="Addy" last-name="Osmani" url="https://addyosmani.com/">}}</span>.
[^8]: Firefox users [can enable "find as you type"](https://website-archive.mozilla.org/www.mozilla.org/access/access/type-ahead/) by toggling a preference in <samp>about:<wbr>config</samp>. Chromium (and derivatives) users can [install an extension](https://github.com/Foxy/chrome-type-ahead); note that it requires full-page access and performs script injection to work. [^9]: Firefox users [can enable "find as you type"](https://website-archive.mozilla.org/www.mozilla.org/access/access/type-ahead/) by toggling a preference in <samp>about:<wbr>config</samp>. Chromium (and derivatives) users can [install an extension](https://github.com/Foxy/chrome-type-ahead); note that it requires full-page access and performs script injection to work.
[^9]: Iterating through a list of font names to see if each one is available on a user's system is a slow but effective way to determine installed fonts without being granted permission to use the Font Access API. [Browser&shy;Leaks has a demo](https://browserleaks.com/fonts) of this approach. Warning: the page might hog your CPU for a while. [^10]: Iterating through a list of font names to see if each one is available on a user's system is a slow but effective way to determine installed fonts without being granted permission to use the Font Access API. [Browser&shy;Leaks has a demo](https://browserleaks.com/fonts) of this approach. Warning: the page might hog your CPU for a while.
[^10]: Decoration is more than cosmetic. The [color overrides and accessibility](#color-overrides-and-accessibility) sub-section describes how some decorations, like borders, improve access&shy;ibility. [^11]: Decoration is more than cosmetic. The [color overrides and accessibility](#color-overrides-and-accessibility) sub-section describes how some decorations, like borders, improve access&shy;ibility.
[^11]: uBlock Origin is a popular browser extension for content filtering; it's the most popular Firefox add-on. It includes a built-in feature to block all media elements exceeding a user-configurable size threshold. [^12]: uBlock Origin is a popular browser extension for content filtering; it's the most popular Firefox add-on. It includes a built-in feature to block all media elements exceeding a user-configurable size threshold.
[^12]: [WebAIM](https://wave.webaim.org/api/docs?format=html) and the [University of Illinois](https://fae.disability.illinois.edu/rulesets/IMAGE_4_EN/) recommend 100 characters; [Tangaru](https://www.tanaguru.com/en/) recommends an even smaller limit of 80 characters. I sometimes exceed 100 characters for detailed images but usually stay below 80. [^13]: [WebAIM](https://wave.webaim.org/api/docs?format=html) and the [University of Illinois](https://fae.disability.illinois.edu/rulesets/IMAGE_4_EN/) recommend 100 characters; [Tangaru](https://www.tanaguru.com/en/) recommends an even smaller limit of 80 characters. I sometimes exceed 100 characters for detailed images but usually stay below 80.
[^13]: Once it gains basic support across all browsers and screen readers, I might recommend using `aria-details` instead of <code>aria-<wbr>des&shy;cribedby</code> for more complex descriptions. Right now, [`aria-details` is only supported by JAWS](https://a11ysupport.io/tech/aria/aria-details_attribute). <span itemprop="mentions" itemscope itemtype="https://schema.org/TechArticle">{{<cited-work name="WAI-ARIA 1.2" url="https://www.w3.org/TR/wai-aria-1.2/#aria-details">}}</span> describes `aria-details` with an example similar to the one I gave in [code snippet 5](#xkcd-html). [^14]: Once it gains basic support across all browsers and screen readers, I might recommend using `aria-details` instead of <code>aria-<wbr>des&shy;cribedby</code> for more complex descriptions. Right now, [`aria-details` is only supported by JAWS](https://a11ysupport.io/tech/aria/aria-details_attribute). <span itemprop="mentions" itemscope itemtype="https://schema.org/TechArticle">{{<cited-work name="WAI-ARIA 1.2" url="https://www.w3.org/TR/wai-aria-1.2/#aria-details">}}</span> describes `aria-details` with an example similar to the one I gave in [code snippet 5](#xkcd-html).
[^14]: Since <abbr title="Windows High Contrast Mode">WHCM</abbr> sets colors indepen&shy;dently of explicitly-defined ARIA roles, it's a good way to test adherence to [the First Rule of ARIA](#first-rule-of-aria). [^15]: Since <abbr title="Windows High Contrast Mode">WHCM</abbr> sets colors indepen&shy;dently of explicitly-defined ARIA roles, it's a good way to test adherence to [the First Rule of ARIA](#first-rule-of-aria).
[^15]: When making an earlier version of this site's dark-mode color palette, I made the mistake of exclusively testing in cheap or poorly-calibrated displays with bright black points. I mistakenly thought that my `#0b0b0b` background was bright enough to [prevent halation](#halation). Only after testing on a better screen did I realize that it would look almost completely black; I subsequently lightened the background to `#111` to strike a good compromise. [^16]: When making an earlier version of this site's dark-mode color palette, I made the mistake of exclusively testing in cheap or poorly-calibrated displays with bright black points. I mistakenly thought that my `#0b0b0b` background was bright enough to [prevent halation](#halation). Only after testing on a better screen did I realize that it would look almost completely black; I subsequently lightened the background to `#111` to strike a good compromise.
[^16]: <span itemprop="mentions" itemscope itemtype="https://schema.org/Book">{{<cited-work name="Practical Typography" url="https://practicaltypography.com/">}}</span> only renders invisible text without JavaScript. You can use a textual browser, screen reader, copy-paste the page contents elsewhere, use a reader-mode implemen&shy;tation, or "view source" to read it without enabling scripts. All of these options will ironically override the carefully-crafted typography of this website about typography. [^17]: <span itemprop="mentions" itemscope itemtype="https://schema.org/Book">{{<cited-work name="Practical Typography" url="https://practicaltypography.com/">}}</span> only renders invisible text without JavaScript. You can use a textual browser, screen reader, copy-paste the page contents elsewhere, use a reader-mode implemen&shy;tation, or "view source" to read it without enabling scripts. All of these options will ironically override the carefully-crafted typography of this website about typography.
I find <cite>Practical Typography</cite> quite useful for printed works, and incorporated a more moderate version of its advice on soft-hyphens into this page. With a few such exceptions, I generally find it to be poor advice for Web content. I find <cite>Practical Typography</cite> quite useful for printed works, and incorporated a more moderate version of its advice on soft-hyphens into this page. With a few such exceptions, I generally find it to be poor advice for Web content.
[^17]: libavif links against libaom, librav1e, and/or libsvtav1 to perform AVIF encoding and decoding. libaom is best for this use-case, particularly since libaom can link against libjxl to use its Butteraugli distortion metric. This lets libaom optimize the perceptual quality of lossy encodes much more accu&shy;rately. [^18]: libavif links against libaom, librav1e, and/or libsvtav1 to perform AVIF encoding and decoding. libaom is best for this use-case, particularly since libaom can link against libjxl to use its Butteraugli distortion metric. This lets libaom optimize the perceptual quality of lossy encodes much more accu&shy;rately.
[^18]: ATs typically let users navigate by headings, landmarks, paragraphs, and links. Most users prefer skipping article content with heading-based navigation. Keyboard users can bind different keys to different modes of navigation, but mobile users can only access one navigation mode at a time. [^19]: ATs typically let users navigate by headings, landmarks, paragraphs, and links. Most users prefer skipping article content with heading-based navigation. Keyboard users can bind different keys to different modes of navigation, but mobile users can only access one navigation mode at a time.
Mobile users wishing to temporarily switch modes have to stop, change their navigation mode, perform a navigation gesture, and switch back. Mobile users trying to skim an article don't always find this worth the effort and sometimes stick to heading-based navigation even when a different mode would be optimal. Mobile users wishing to temporarily switch modes have to stop, change their navigation mode, perform a navigation gesture, and switch back. Mobile users trying to skim an article don't always find this worth the effort and sometimes stick to heading-based navigation even when a different mode would be optimal.
[^19]: If you'd like to learn more, <span itemprop="mentions" itemscope itemtype="https://schema.org/BlogPosting">{{< cited-work name="A guide to designing accessible, WCAG-compliant focus indicators" url="https://www.sarasoueidan.com/blog/focus-indicators/" extraName="headline" >}} by {{< indieweb-person url="https://www.sarasoueidan.com/" first-name="Sara" last-name="Soueidan" url="https://www.sarasoueidan.com/" itemprop="author">}}</span> has far more details on making accessible focus indicators. [^20]: If you'd like to learn more, <span itemprop="mentions" itemscope itemtype="https://schema.org/BlogPosting">{{< cited-work name="A guide to designing accessible, WCAG-compliant focus indicators" url="https://www.sarasoueidan.com/blog/focus-indicators/" extraName="headline" >}} by {{< indieweb-person url="https://www.sarasoueidan.com/" first-name="Sara" last-name="Soueidan" url="https://www.sarasoueidan.com/" itemprop="author">}}</span> has far more details on making accessible focus indicators.
[^20]: Screen readers aren't alone here. Several programs strip inline formatting: certain feed readers, search result snippets, and textual browsers invoked with the `-dump` flag are some examples I use every day. [^21]: Screen readers aren't alone here. Several programs strip inline formatting: certain feed readers, search result snippets, and textual browsers invoked with the `-dump` flag are some examples I use every day.
[^21]: I excluded PageSpeed Insights and GTMetrix since those are mostly covered by Lighthouse. I excluded Security Headers, since its approach seems to be recommen&shy;ding headers regardless of whether or not they are necessary. It penalizes forgoing the <code>Per&shy;missions-<wbr>Policy</code> header even if the CSP blocks script loading and execution; see [Security Headers issue #103](https://github.com/securityheaders/securityheaders-bugs/issues/103). I personally find the <code>Per&shy;missions-<wbr>Policy</code> header quite problematic, as I noted in August 2021 on [webappsec-permissions-policy issue #189](https://github.com/w3c/webappsec-permissions-policy/issues/189#issuecomment-904783021). [^22]: I excluded PageSpeed Insights and GTMetrix since those are mostly covered by Lighthouse. I excluded Security Headers, since its approach seems to be recommen&shy;ding headers regardless of whether or not they are necessary. It penalizes forgoing the <code>Per&shy;missions-<wbr>Policy</code> header even if the CSP blocks script loading and execution; see [Security Headers issue #103](https://github.com/securityheaders/securityheaders-bugs/issues/103). I personally find the <code>Per&shy;missions-<wbr>Policy</code> header quite problematic, as I noted in August 2021 on [webappsec-permissions-policy issue #189](https://github.com/w3c/webappsec-permissions-policy/issues/189#issuecomment-904783021).
[^22]: My site caches HTML documents for ten minutes and caches the RSS feed for several hours. I disagree with webhint's recommen&shy;dations against this: cache durations should be based on request rates and how often a resource is updated. I also disagree with some of its `content-type` recommen&shy;dations: you don't need to declare UTF-8 charsets for SVG content-type headers if the SVG is ASCII-only and called from a UTF-8 HTML document. You gain nothing but header bloat by doing so. [^23]: My site caches HTML documents for ten minutes and caches the RSS feed for several hours. I disagree with webhint's recommen&shy;dations against this: cache durations should be based on request rates and how often a resource is updated. I also disagree with some of its `content-type` recommen&shy;dations: you don't need to declare UTF-8 charsets for SVG content-type headers if the SVG is ASCII-only and called from a UTF-8 HTML document. You gain nothing but header bloat by doing so.
[^23]: Consider disabling the JIT for your normal browsing too; doing so removes whole classes of vulnera&shy;bilities. In Firefox, navigate to <samp>about:<wbr>config</samp> and toggle some flags under <code>javascript<wbr>.options</code>. [^24]: Consider disabling the JIT for your normal browsing too; doing so removes whole classes of vulnera&shy;bilities. In Firefox, navigate to <samp>about:<wbr>config</samp> and toggle some flags under <code>javascript<wbr>.options</code>.
<figure itemprop="hasPart" itemscope itemtype="https://schema.org/SoftwareSourceCode"> <figure itemprop="hasPart" itemscope itemtype="https://schema.org/SoftwareSourceCode">
<figcaption> <figcaption>
@ -1610,7 +1614,7 @@ A special thanks goes out to GothAlice for the questions she answered in <samp>#
In Chromium and derivatives, run the browser with `--js-flags='--jitless'`; in the Tor Browser, set the security level to "Safer". In Chromium and derivatives, run the browser with `--js-flags='--jitless'`; in the Tor Browser, set the security level to "Safer".
[^24]: LibreOffice can also render HTML but has extremely limited support for CSS. OnlyOffice seems to work best, but doesn't load images. If your page is CSS-optional, it should look fine in both. [^25]: LibreOffice can also render HTML but has extremely limited support for CSS. OnlyOffice seems to work best, but doesn't load images. If your page is CSS-optional, it should look fine in both.
Fun fact: Microsoft Outlook renders HTML email with Microsoft Word's proprietary HTML engine. Fun fact: Microsoft Outlook renders HTML email with Microsoft Word's proprietary HTML engine.