A web font strategy
The Session has been online in some form since the late 1990s. That’s long before web fonts existed.
To begin with, Times New Roman was the only game in town if you wanted serif type on a website. When Microsoft introduced Georgia it was a godsend. A beautiful typeface designed by Matthew Carter for the screen. I put it right at the start of my font stack for The Session.
Later, web fonts came along. Boy, does that short sentence belie the drama! There were very heated discussions about whether web browsers should provide this ability at all, and what it would mean for type foundries.
Microsoft led the way with their prorietary EOT format. Then everyone agreed on WOFF. Finally we got WOFF2, Electric Boogaloo.
Perhaps more important than that, we got intermediaries. Typekit, Fontdeck, and then the big daddy, Google Fonts.
That’s pretty much the state of play today. Oh yeah, and we’ve got variable fonts now.
I remember Nick Sherman presenting the idea of variable fonts at an Ampersand event years ago. I remember thinking “great idea, but it’ll never happen.” Pure science fiction. I thought the same thing when I first saw a conference presentation about a miraculous image format called Scalable Vector Graphics.
Sometimes I like to stop and take stock of what we take for granted in web browsers now. Web fonts. Variable web fonts. SVG. Flexbox. Grid. Media queries. Container queries. Fluid typography. And I haven’t even mentioned how we were once limited to just 216 colours on the web.
Georgia
Given all the advances in web typography, you might be wondering how my font strategy for The Session changed over the years.
It didn’t.
I mean, sure, I added fluid typography. That was a natural extension of my love for liquid layouts and, later, responsive design. But the font stack itself? That was still Georgia all the way.
Y’see, performance has always been a top priority for The Session. If I was going to replace a system font with a web font that the user had to download, it really needed to be worth it.
Over the years I dabbled with different typefaces but none of them felt quite right to me. And I still think Georgia is a beautiful typeface.
“But your website will look like lots of other websites!” some may cry. That used to be true when all we had was system fonts. But now that web fonts have become the norm, it’s actually pretty unusual to see Georgia in the wild.
Lora
Recently I found a font I liked. Part of why I like it is that it shares a lot of qualities with Georgia. It’s Lora by Olga Karpushina and Alexei Vanyashin.
I started to dabble with it and began seriously contemplating using it on The Session.
It’s a variable font, which is great. But actually, I’m not using that many weights on The Session. I could potentially just use a non-variable variety. It comes in fixed weights of regular, medium, semibold, and bold.
Alas, the regular weight (400) is a bit too light and the medium weight (500) is a bit too heavy. My goldilocks font weight is more like 450.
Okay, so the variable font it is. That also allows me to play around with some subtle variations in weights. As the font size gets bigger for headings, the font weight can reduce ever so slightly. And I can adjust the overall font weight down in dark mode (there’s no grading feature in this font, alas).
Subsetting
Lora supports a lot of alphabets, which is great—quite a few alphabets turn up on The Session occasionally. But this means that the font file size is quite large. 84K.
Subsetting to the rescue!
I created a subset of Lora that has everything except Cyrillic, Greek, and Latin Extended-B. I created another subset that only has Cyrillic, Greek, and Latin Extended-B. Now I’ve got two separate font files that are 48K and 41K in size.
I wrote two @font-face declarations for the two files. They’ve got the same font-family (Lora), the same font-weight (400 700), and the same font-style (normal) but they’ve got different values for unicode-range. That way, browsers know to only use appropriate file when characters on the page actually match the unicode range.
The first file is definitely going to be used. The second one might not even be needed on most pages.
I want to prioritise the loading of that first subsetted font file so it gets referenced in a link element with rel="preload".
The switcheroo
As well as file size, my other concern was how the swapping from Georgia to Lora would be perceived, especially on a slow connection. I wanted to avoid any visible rejiggering of the content.
This is where size-adjust comes in, along with its compadres ascent-override and descent-override.
Rather than adjusting the default size of Lora to match that of Georgia, I want to do it the other way around; adjust the fallback font to match the web font.
Here’s how I’m doing it:
@font-face {
font-family: 'Fallback for Lora';
src: local('Georgia');
size-adjust: 105.77%;
ascent-override: 95.11%;
descent-override: 25.9%;
}
And then my font stack is:
font-family: Lora, 'Fallback for Lora', Georgia, serif;
It’s highly unlikely that any device out there has a system font called “Fallback for Lora” so I can be pretty confident that the @font-face adjustment rules will only get applied to browsers that have the right local font, Georgia.
But where did those magic numbers come from for size-adjust, ascent-override, and descent-override?
They came from Katie Hempenius. As well as maintaing a repo of font metrics, she provides the formula needed to calculate all three values. Or you could use this handy tool to eyeball it.
With that, Georgia gets swapped out for Lora with a minimum of layout shift.
First-timers and repeat visitors
Even with the layout shift taken care of, do I want to serve up web fonts to someone on a slow connection?
It depends. Specifically, it depends on whether it’s their first time visiting.
The Session already treats first time visitors differently to repeat visitors. The first time you visit the site, critical CSS is embedded in the head of the HTML page instead of being referenced in an external style sheet. Only once the page has loaded does the full style sheet also get downloaded and cached.
I decided that my @font-face rules pointing to the web fonts are not critical CSS. If it’s your first time visiting, those CSS rules only get downloaded after the page is done loading.
And unless you’re on a fast connection, you won’t see Georgia get swapped out for Lora. That’s because I’ve gone with a font-display value of “optional”.
Most people use “swap”. Some people use “fallback”. You’ve got to be pretty hardcore to use “optional”.
But the next page you go to, or the next time you come to the site, you more than likely will see Lora straight away. That’s because of the service worker I’ve got quietly putting static assets into the Cache API: CSS, JavaScript, and now web fonts.
So even though I’m prioritising snappy performance over visual consistency, it’s a trade-off that only really comes into play for first visits.
Next
I’m pretty happy with the overall strategy. Still, I’m not going to just set it and forget it. I’ll be monitoring the CRUX data for The Session keeping a particular eye on cumulative layout shift.
Before adding web fonts, the cumulative layout shift on The Session was zero. I think I’ve taken all the necessary steps to keep it nice and low, but if I’m wrong I’ll need to revisit my strategy.
Update: Big thanks to Roel Nieskens—of Wakamai Fondue fame—who managed to get the file size of my main subsetted font down even further; bedankt!