The Font Loading Checklist
When I look back at the last four years that I’ve spent learning everything I could about web fonts and how web fonts load, I can distill it all down to a small checklist of ideals that I continue to chase. Our goal as web developers is to maximize the experience and raise user expectations to the level of what the web is capable of delivering, but also to manage our performance budgets to ensure that we are fulfilling the promise of the web—it’s ubiquity. This checklist should help you deliver on those two often competing ideals.
The Font Loading Checklist
(Start a Web Font load)
Web fonts don’t start downloading until they’re found to be used in content, so it’s often late in the page load. We need to tell the browser to start downloading our high priority web fonts sooner.
- Strategy: Use
preload
(Behavior while a Web Font is loading)
This means absolutely no invisible text. This is known as the flash of invisible text, or FOIT. We can use flash of unstyled text (FOUT) strategies to prioritize system fonts during web font load.
- Strategy: Use
font-display
- Strategy: Use the CSS Font Loading API
(Reduce Web Font load time)
Guess what: Smaller file downloads finish sooner.
- Strategy: Use
WOFF2
formats (compression built in) - Strategy: Subset your fonts, if language and licensing requirements allow.
Check out Glyphhanger to help with both of these strategies.
(Behavior after a Web Font has loaded)
Each independent @font-face
block has its own loading life-cycle. Its own FOIT, its own FOUT, its own repaint and reflow. When using two or more web fonts for a single family, its important to group the repaints together to reduce reflow of text on your page.
- Strategy: Use the CSS Font Loading API to group your repaints.
- Strategy: Use Variable fonts (Browser support at Can I Use: Variable Fonts)
7 Comments
@zellwk
Let me do what I do best here: Make scary things approachable and friendly :) @zachleat Ok with viewing a preview (when I'm done) before I release the post to the public?
@zachleat
(sounds good!)
@leeerob
Thank you for your posts on web fonts 🙏 They really helped me learn and understand all the tradeoffs.
@zachleat
Yay! I’m really glad to see someone picking up the torch there 🏆
@zachleat
this is the best advice I can give you: zachleat.com/web/font-check…
@lyeuhm
I've done none of these so, great starting point. 🤣 Thanks Zach <3
@zachleat
haha