web-font-loading-recipes
A bunch of demos for different web font loading strategies. Some of these are included on A Comprehensive Guide to Font Loading Strategies, some of them are more experimental.
Demos are hosted at https://www.zachleat.com/web-fonts/demos/
Table of Contents
Recommended Methods
As web fonts are a progressive enhancement and with increasing support for the CSS Font Loading API, we can look forward to a time in which we won’t need to inline a polyfill into the header (for even faster font loading). The simplified CSS Font Loading API recipes are the defaults, but polyfilled versions are included for broader browser support—notably only the polyfilled versions will show web fonts in Internet Explorer and Edge web browsers (which do not have support for the CSS Font Loading API).
font-display: swap
preload
font-display: swap with preload
FOUT with a Class
FOUT
Similar to the above, but without using a class—using only the CSS Font Loading API. This doesn’t require any modification of the CSS, injects the web fonts using JS programmatically. I first saw this method in the Webfont Handbook from @bramstein.
- JavaScript: CSS Font Loading API
- Code
- Demo (4 web fonts)
- Related:
.style.fontFamily method (only works well with one family per page), first saw this in a tweet from @simevidas
FOFT
Two stage load, using one Roman font file in the first stage (with font-synthesis).
Critical FOFT
Critical FOFT with Data URI
Critical FOFT with preload
The eBay Method
“The Compromise”: Critical FOFT with preload, with a polyfill fallback emulating font-display: optional
Further Enhancements
These aren’t necessarily font loading strategies on their own but they are extra enhancements you can layer on top of and pair with existing strategies.
Opt out of web fonts on slow connection speeds.
prefers-reduced-motion User Preference
Opt out of web fonts when user has enabled Reduce Motion accessibility preference.
save-data User Preference
Opt out of web fonts when user has enabled Data Saver mode.
Experiments in Progress
You’ll probably see blog posts on these at some point.
Not Recommended but included for Posterity
font-display: optional
- A little harsh to put this in the Not Recommended section but I like my web fonts on an empty-cache visit 😎
- Code
- Demo** (4 web fonts)
System fonts
C’mon. 😇
Unceremonious Web Fonts
Unceremonious Web Fonts, WOFF2 Only (Cutting the Mustard)
Old browsers used to render FOIT without a timeout, which in practice made web fonts a single point of failure. Using WOFF2 only cuts the mustard to modern browsers that have a three second FOIT timeout for web fonts. We’re anti-invisible text here, but this approach is worth mentioning.
Unceremonious Faux Web Fonts
font-synthesis is not a good end-product.
Anti-patterns and Deprecated Methods
⚠️ Inline Data URI
⚠️ Asynchronous Data URI
⚠️ <style> Injection
Anything that uses JavaScript to inject a new <style> with @font-face blocks inside. Really bad repaint cost—avoid this. This is used in the Asynchronous Data URI method above but is also common in worse-performing methods too.
⚠️ font-display: optional and preload
⚠️ FOFT using only font-display (mixing font-display values across a font-family)
This method does not currently have cross-browser support. I’m hoping this will change—learn more.
- Code
- Demo** (4 web fonts—1
swap / 3 optional)
Failed Experiments
🚫 Asynchronous CSS
This is a common thing people try—they asynchronously load the CSS (and only the CSS). Heck, I used this behavior before I started studying web font loading.
🚫 @supports and font-display
- Reasons for trying:
- might be nice to only use web fonts if you can FOUT with
font-display
- might be nice to have FOUT with a class if
font-display not supported (and work well without JS dependencies)
- Failed:
@supports doesn’t work with font-face descriptors.
- Code
- Demo
🚫 font-family Stack
-
Put two or more font-family web fonts in a single font-family stack.
-
Failed: The font matching algorithm selects the first web font that matches and attempts to load it (ignoring subsequent web font families). Even if you preload the subset first stage, it’ll swap over due to font-family order priority.
-
Code
-
Demo
-
Update: While you can mitigate the above problem with font-display, perhaps modifying the order of the font-family stack and @font-face block ordering, there are still problems with removing the unnecessary subset web font from the page after the larger version has loaded. Font features that occur with glyphs that cross these font file boundaries will be broken (kerning, ligatures, et cetera). Relatedly, you cannot remove a CSS-paired FontFace object using the CSS Font Loading API (per the specification).
** Take note that these methods will FOUT in Internet Explorer and Edge by taking advantage of their default font loading behavior.
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