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New subsection on cache, semantic code snippets
Add "Don't count on the cache" under the "Optimal loading" section. Some semantics for code snippets, including switching some from <code> to <samp>.
This commit is contained in:
Rohan Kumar
parent
89f04e2f31
commit
069dca0a06
3 changed files with 65 additions and 35 deletions
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@ -93,7 +93,8 @@ nav li,
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* font size preferences. */
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code,
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pre,
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kbd {
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kbd,
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samp {
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/* stylelint-disable -- compatibility hack */
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font-family: monospace, monospace;
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@ -133,6 +133,27 @@ My website includes a "link" header to load an SVG that serves as my IndieWeb ph
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```
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link: </favicon.072dbf7bc4323646b9ee96243fbd71b2.svg>; rel=preload; as=image
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```
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### Don't count on the cache
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The browser cache is a valuable tool to save bandwidth and improve page speed, but it's not as reliable as many people seem to believe. Don't focus too much on "repeat view" performance.
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Out of privacy concerns, most browsers no longer re-use cached content across sites; refer back to the "third-party content" section for more details. Privacy-conscious users (including all users using "private" or "incognito" sessions) will likely have their caches wiped between sessions. Don't focus too much on "repeat view" performance until after your "initial view" performance is good enough.
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Furthermore: a high number of cached resources can decrease performance of the cache, causing browsers to bypass the cache:
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=> https://simonhearne.com/2020/network-faster-than-cache When Network is Faster than Cache
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The effect is especially pronounced on low-end phones and mechanical hard drives.
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One way to help browsers decide which disk-cached resources to prioritize is to use immutable assets. Include the `immutable` directive in your cache-control headers, and cache-bust modified assets by changing their URLs.
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The only external assets on my pages are images and a web app manifest (for icons); I mark these assets as "immutable" and cache-bust them by including checksums in their filenames:
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```
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cache-control: max-age=31557600, immutable
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```
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You can also keep your asset counts low by combining textual assets (e.g. CSS) and inlining small resources.
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### Inline content
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@ -68,12 +68,11 @@ JavaScript and WebAssembly are responsible for the bulk of modern web exploits.
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<figure itemscope itemtype="https://schema.org/SoftwareSourceCode">
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<figcaption>
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<span itemprop="codeSampleType">Code snippet</span>: this is the CSP for my main website.
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<strong itemprop="codeSampleType">Code snippet</strong>: this is the CSP for my main website.
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</figcaption>
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```
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default-src 'none';
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<pre><samp itemprop="text">default-src 'none';
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img-src 'self' data:;
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style-src 'sha256-3U3TNinhti/dtVz2/wuS3peJDYYN8Yym+JcakOiXVes=';
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style-src-attr 'none';
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@ -82,8 +81,7 @@ base-uri 'none';
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form-action 'none';
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manifest-src https://seirdy.one/manifest.min.ca9097c5e38b68514ddcee23bc6d4d62.webmanifest;
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upgrade-insecure-requests;
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sandbox allow-same-origin
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```
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sandbox allow-same-origin</samp></pre>
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</figure>
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@ -148,16 +146,33 @@ HTML is a blocking resource: images and stylesheets will not load until the user
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<figure itemscope itemtype="https://schema.org/SoftwareSourceCode">
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<figcaption>
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<span itemprop="codeSampleType">Code snippet</span>: my website includes a `link` header to load an SVG that serves as my IndieWeb photo and favicon:
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<strong itemprop="codeSampleType">Code snippet</strong>: my website includes a `link` header to load an SVG that serves as my IndieWeb photo and favicon:
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</figcaption>
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```
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link: </favicon.072dbf7bc4323646b9ee96243fbd71b2.svg>; rel=preload; as=image
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```
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<pre><samp itemprop="text">link: </favicon.072dbf7bc4323646b9ee96243fbd71b2.svg>; rel=preload; as=image</samp></pre>
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</figure>
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### Don't count on the cache
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The browser cache is a valuable tool to save bandwidth and improve page speed, but it's not as reliable as many people seem to believe. Don't focus too much on "repeat view" performance.
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Out of privacy concerns, most browsers no longer re-use cached content across sites; refer back to the section on [third-party content](#third-party-content) for more details. Privacy-conscious users (including all users using "private" or "incognito" sessions) will likely have their caches wiped between sessions.
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Requesting a high number of cached resources can decrease performance of the cache, causing browsers to [bypass the cache](https://simonhearne.com/2020/network-faster-than-cache/). The effect is especially pronounced on low-end phones and mechanical hard drives.
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One way to help browsers decide which disk-cached resources to prioritize is to use immutable assets. Include the `immutable` directive in your cache-control headers, and cache-bust modified assets by changing their URLs.
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<figure itemscope itemtype="https://schema.org/SoftwareSourceCode">
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<figcaption>
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<strong itemprop="codeSampleType">Code snippet</strong>: The only external assets on my pages are images and a web app manifest (for icons); I mark these assets as "immutable" and cache-bust them by including checksums in their filenames.
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</figcaption>
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<pre><samp itemprop="text">cache-control: max-age=31557600, immutable</samp></pre>
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</figure>
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You can also keep your asset counts low by combining textual assets (e.g. CSS) and inlining small resources.
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### Inline content
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In addition to HTML, CSS is also a blocking resource. You could pre-load your CSS using a `link` header. Alternatively: if your gzipped CSS is under **one kilobyte,** consider inlining it in the `<head>` using a `<style>` element. Simply inlining stylesheets can pose a security threat, but the `style-src` <abbr title="Content Security Policy">CSP</abbr> directive can mitigate this if you include a hash of your inline stylesheet sans trailing whitespace.
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@ -227,7 +242,7 @@ In-depth server configuration is a bit out of scope, so I'll keep each improveme
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Compression--especially static compression--dramatically reduces download sizes. My full-text RSS feed is about a quarter of a megabyte, but the Brotli-compressed version is around 70 kilobytes. Caddy supports this with a `precompressed` directive; Nginx requires a [separate module](https://github.com/google/ngx_brotli) for Brotli compression.
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When serving many resources at once (e.g., if a page has many images), HTTP/2 could offer a speed boost through multiplexing. HTTP/3 is unlikely to help textual websites much, so run a benchmark to see if it's worthwhile.
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When serving many resources at once (e.g., if a page has many images), HTTP/2 could offer a speed boost through multiplexing; use it if you can, but expect many clients to only support HTTP/1.1. HTTP/3 is unlikely to help textual websites much, so run a benchmark to see if it's worthwhile.
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Consider caching static assets indefinitely with a year-long duration in the "cache-control" header, possibly with an `immutable` parameter. If you have to update a static asset, cache-bust it by altering the URL. This approach should eliminate the need for an `etag` header on static assets.
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@ -403,14 +418,10 @@ In your stylesheets, _avoid using `px`_ where possible. Define sizes and dimensi
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<figure itemscope itemtype="https://schema.org/SoftwareSourceCode">
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<figcaption>
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<span itemprop="codeSampleType">Code snippet</span>: set font size and line-spacing with a percentage and a unitless value, respectively.
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<strong itemprop="codeSampleType">Code snippet</strong>: set font size and line-spacing with a percentage and a unitless value, respectively.
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</figcaption>
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```
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font: 100%/1.5 sans-serif;
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```
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<pre><code itemprop="text">font: 100%/1.5 sans-serif;</code></pre>
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</figure>
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Beyond alt-text
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@ -652,14 +663,13 @@ Most of my images will probably be screenshots that start as PNGs. My typical fl
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<figure id="png-pipeline" itemscope itemtype="https://schema.org/SoftwareSourceCode">
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<figcaption>
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<span itemprop="codeSampleType">Code snippet</span>: this is a sample command to compress a PNG image using ImageMagick, `pngquant`, and `oxipng`. It shrinks the image, turns it grayscale, reduces the color palette, and then applies lossless Zopfli compression.
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<strong itemprop="codeSampleType">Code snippet</strong>: this is a sample command to compress a PNG image using ImageMagick, `pngquant`, and `oxipng`. It shrinks the image, turns it grayscale, reduces the color palette, and then applies lossless Zopfli compression.
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</figcaption>
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<pre>
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<code>convert <var translate="yes">ORIGINAL_FILE</var> \
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-resize 75% -colorspace gray -format png - \
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| pngquant -s 1 12 - \
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<pre><code itemprop="text">convert <var translate="yes">ORIGINAL_FILE</var> \
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-resize 75% -colorspace gray -format png - \
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| pngquant -s 1 12 - \
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| oxipng -o max -Z --fix - --out <var translate="yes">OUTPUT_FILE</var>
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</code></pre>
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@ -694,11 +704,11 @@ A `<picture>` element allows selection of sources based on any CSS media query.
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<figure itemscope itemtype="https://schema.org/SoftwareSourceCode">
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<figcaption>
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<span itemprop="codeSampleType">Code snippet</span>: a minimal example of a <code>picture</code> containing a dark variant:
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<strong itemprop="codeSampleType">Code snippet</strong>: a minimal example of a <code>picture</code> containing a dark variant:
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</figcaption>
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<pre>
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<code><picture>
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<code itemprop="text"><picture>
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<source type="image/png"
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srcset="/p/dark.png"
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media="screen and (prefers-color-scheme: dark)">
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@ -736,17 +746,15 @@ Exceptions exist: one or two very simple responsive changes won't hurt. The main
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<figure itemscope itemtype="https://schema.org/SoftwareSourceCode">
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<figcaption>
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<span itemprop="codeSampleType">Code snippet</span>: the only responsive layout change on [my website](https://seirdy.one/) is a single CSS declaration to switch between inline and multi-line navigation links at the top of the page:
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<strong itemprop="codeSampleType">Code snippet</strong>: the only responsive layout change on [my website](https://seirdy.one/) is a single CSS declaration to switch between inline and multi-line navigation links at the top of the page:
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</figcaption>
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```
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@media print, (min-width: 32rem) {
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<pre><code itemprop="text">@media print, (min-width: 32rem) {
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header nav li {
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display: inline;
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}
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}
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```
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}</code></pre>
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</figure>
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@ -789,11 +797,10 @@ When setting max line lengths, use a CSS media query to ensure that printed vers
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<figure itemscope itemtype="https://schema.org/SoftwareSourceCode">
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<figcaption>
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<span itemprop="codeSampleType">Code snippet</span>: I opted to wrap all max-width rules in a media query to ensure that they only get called for the <code>screen</code> media type:
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<strong itemprop="codeSampleType">Code snippet</strong>: I opted to wrap all max-width rules in a media query to ensure that they only get called for the <code>screen</code> media type:
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</figcaption>
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```
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@media screen {
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<pre><code itemprop="text">@media screen {
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html {
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max-width: 45em;
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padding: 0 3%;
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@ -803,8 +810,7 @@ When setting max line lengths, use a CSS media query to ensure that printed vers
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margin: auto;
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max-width: 38em;
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}
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}
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```
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}</code></pre>
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</figure>
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@ -1146,6 +1152,8 @@ A special thanks goes out to GothAlice for the questions she answered in `#webde
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[^10]: 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 accurately.
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[^11]: <p>Consider disabling the JIT for your normal browsing too; doing so removes whole classes of vulnera­bilities. In Firefox, navigate to <code>about:config</code> and toggle these options:</p><pre><code>javascript.options.ion<br>javascript.options.baselinejit<br>javascript.options.native_regexp<br>javascript.options.asmjs<br>javascript.options.wasm</code></pre><p>In Chromium and derivatives, run the browser with <code>--js-flags='--jitless'</code>; in the Tor Browser, set the security level to "Safer".
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[^11]: <p>Consider disabling the JIT for your normal browsing too; doing so removes whole classes of vulnera­bilities. In Firefox, navigate to <code>about:config</code> and toggle some flags under <code>javascript.options</code>.</p><figure itemscope itemtype="https://schema.org/SoftwareSourceCode"><figcaption><strong itemprop="codeSampleType">Code snippet</strong>: Firefox prefs to turn off JIT compilation</figcaption><pre><code itemprop="text">javascript.options.ion<br>javascript.options.baselinejit<br>javascript.options.native_regexp<br>javascript.options.asmjs<br>javascript.options.wasm</code></pre></figure><p>
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In Chromium and derivatives, run the browser with `--js-flags='--jitless'`; in the Tor Browser, set the security level to "Safer".
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