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/

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

• Code
• Read more
• Demo** (4 web fonts)

preload

• Code
• Read more
• Demo** (4 web fonts—1 preloaded)

font-display: swap with preload

• Code
• Read more about font-display and preload
• Demo** (4 web fonts—1 preloaded)

FOUT with a Class

• Code
• Read more
• Demo (4 web fonts)
• or using a polyfill—Demo (4 web fonts)

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.

• 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

• Code
• Read more
• Demo (5 web fonts, two are the same—but only loaded once)
• or using a polyfill—Demo (4 web fonts)

FOFT using only font-display (mix font-display values)

• Code
• Demo (4 web fonts—1 swap / 3 optional)
• ⚠️ This method does not currently have cross-browser support. I’m hoping this will change—learn more.

Critical FOFT

• Code
• Read more
• Demo (5 web fonts—1 subset)
• or using a polyfill—Demo (5 web fonts—1 subset)

Critical FOFT with Data URI

• Code
• Read more
• Demo (5 web fonts—1 subset inline Data URI)
• or using a polyfill—Demo (5 web fonts—1 subset inline Data URI)

Critical FOFT with preload

• Code
• Read more
• Demo (5 web fonts—1 subset)
• or using a polyfill—Demo (5 web fonts—1 subset)

The eBay Method

• Code: HTML and Lazy-loaded JavaScript
• Emulate font-display: optional with JavaScript.
  • Notable that it lazy loads the font loading polyfill only if CSS Font Loading API is not supported
• Read more at eBay’s Font Loading Strategy.
• Demo (4 web fonts) (polyfill is lazy loaded when CSS Font Loading API is not supported)

“The Compromise”: Critical FOFT with preload, with a polyfill fallback emulating font-display: optional

• Code: HTML and Lazy-loaded JavaScript
• Read more
  • Inspired by the eBay method above.
• Demo (5 web fonts—1 subset) (polyfill is lazy loaded when CSS Font Loading API is not supported)
• Currently in use on zachleat.com and smashingmagazine.com

Experiments in Progress

You’ll probably see blog posts on these at some point.

• Metric compatible web fonts
  • Show how fonts can look without FOUT reflow if they are metric compatible.
• FOUT metric matching with a Variable Font
  • Reduction in FOUT reflow (reduce text movement on web font render)
  • Related: Font style matcher from @notwaldorf

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
  • Code
  • Documentation
  • Demo (0 web fonts)
• Unceremonious Web Fonts
  • Code
  • Documentation
  • Demo** (4 web fonts)
• Unceremonious Faux Web Fonts
  • Code
  • Demo** (1 web font): Bold and italic variants are rendered using font-synthesis
• Unceremonious Web Fonts, WOFF2 Only (Cutting the Mustard)
  • Code
  • 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. Three seconds is still way too long for me to implement this in production, but it’s worth noting.
  • Demo** (4 web fonts)

Anti-patterns and Deprecated Methods

• ⚠️ Inline Data URI
  • Code
  • Read more
  • Demo (4 web fonts)
• ⚠️ Asynchronous Data URI
  • Code
  • Read more
  • Demo (4 web fonts)
• ⚠️ Anything that injects a new <style> with @font-face blocks inside. Really bad repaint cost—seriously, don’t do this.
• ⚠️ font-display: optional and preload
  • Code
  • Read more: preload with font-display: optional is an Anti-pattern
  • Demo** (4 web fonts)

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.

• Failed: lazy loading the CSS only delays the start of the FOIT. It does not prevent it.
• Read more at Lazy Loading Web Fonts is Probably Not What You Want
• Code (learn more about asynchronous CSS)
• Demo (4 web fonts)

🚫 @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

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** Take note that these methods will FOUT in Internet Explorer and Edge by taking advantage of their default font loading behavior.