The cost of moving from Google Fonts to self-hosted web fonts

Google Fonts has been one of my favorite products on the web of all time. It checks a lot of boxes, and there aren't many reasons for you to not use it.

When you decide to self-host your font files you need to make sure you are delivering them at least as good as them.

# Why is Google Fonts so good?

When you decide to use a custom web font in your project, there are a lot of reasons why going with Google Fonts is a good choice.

The first one is its wide catalog with tons of options legally available.

Another really good feature is the network distribution. When more sites use Google Fonts, bigger are the chances the user has already downloaded the font you included in your project.

Finally, it's font files optimization. The team behind Google Fonts apply really smart compression and subsetting algorithms to shrink font files to small sizes.

They are doing a lot of smart performance optimizations for you. Now, after reading all this, why would someone not use Google Fonts?

It could be the font you want is not in Google Fonts' catalog, or simply you want the benefits of self-hosting your own assets.

# Self-hosting your own fonts

I recently launched a new design for this site, and as part of the release I wanted to push even more performance improvements.

It's fair to say the previous version was using Google Fonts, and was already in good shape, with a perfect score and good numbers in performance measuring tools like Lighthouse.

I described my font strategy several times in articles and talks, which included loading the stylesheet without blocking text content, switching to the custom font only when it is ready, and saving the stylesheet rules with web storage to prevent text flickering while navigating through the site.

Let's see how that strategy changes when you self-hosted your font files.

# Network distribution, cache and headers

The first step is to stop loading Google's stylesheet and move files to your site.

For this redesign I'm using Inter by Rasmus Andersson, so I downloaded the font files into my own assets folder and added the font face rules to my styles.

@font-face {
  font-family: 'Inter';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src:
    url('/assets/fonts/Inter-Regular.woff2') format('woff2'),
    url('/assets/fonts/Inter-Regular.woff') format('woff');
}

@font-face {
  font-family: 'Inter';
  font-style: italic;
  font-weight: 400;
  font-display: swap;
  src:
    url('/assets/fonts/Inter-Italic.woff2') format('woff2'),
    url('/assets/fonts/Inter-Italic.woff') format('woff');
}

We are adding "font-display: swap" to prevent blocking text display to the user while the font files are loading.

I used to load the stylesheet asynchronously with a small amount of JavaScript inlined in the head of the page, to inject its content on forthcoming visits. This, plus browser caching font files prevented flashes on every page navigation.

Now that I'm in control of those font files and font face rules, I'm inlining that CSS straight into the page.

If the amount of font face rules is really big, I would still recommend to put them in a CSS file and load it asynchronously, as an initial flash will always be on the first visit.

With font files under my directory and style rules in place I proceed to navigate through a preview of the site, and to my surprise I see flashes of text on every single navigation.

These flashes are usually a sign of the browser changing the font family of the page because a style has changed or a font file's finished loading.

Looking at the HTTP Headers in the font files that Google delivers, they specify the following rule related to cache control.

cache-control: public, max-age=31536000

Looking at the ones coming from my self-hosted files, the value is the following.

cache-control: public, max-age=0, must-revalidate

The presence of must-revalidate plus max-age=0 tells the browser to fetch the resource on every request and never store the resource in cache.

This is probably the default in my server for this type of asset. The caching strategy is one of the many things Google Fonts handles for us, which needs to be defined on our side now.

As this site is deployed on Netlify, in my netlify.toml configuration file I set the headers for the font assets.

[[headers]]
  for = '/assets/fonts/*'
  [headers.values]
	cache-control = 'public, max-age=31536000'

Depending on what you are using to deploy your site, how you solve this part will be different.

After this change, font files are retrieved from browser cache every time I navigate to a new page, avoiding my text from flickering.

# Font subsetting

On every step of the move, I'm checking performance metrics to make sure nothing is negatively impacting the site. One number that went up badly was page size.

Using Google Fonts the homepage of this site was ~50Kb, but my page weighted ~350Kb with self-hosted font files.

The reason is authors of typefaces usually provide glyphs and features for different usages and languages. Google also optimizes this for a more general usage shrinking file sizes. The best solution to this is to create new font files containing only the glyphs your project needs.

A great way to find out what your font files contain is to visit wakamaifondue and drop them there. You will get a list of all symbols and features.

An important part is knowing the unicode range to cover, basically the group of symbols your project needs. Tools like glyphhanger can crawl pages of your site and return which glyphs they are using.

Another option, especially if you were already using Google Fonts is to rely on the unicode range they use to compress their font files.

UNICODES="U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+2000-206F,U+2074,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD"

From the Inter family, I'm only going to make use of a small group of the features it brings by default.

LAYOUT_FEATURES="kern,ss01,cv05,cv11"

Next step is to use fonttools, a Python library that among other utilities provides a subsetting command. We just need to provide files with .ttf extension.

pyftsubset "src/fonts/Inter-Regular.ttf" --layout-features=$LAYOUT_FEATURES --unicodes=$UNICODES

Font files frequently include hinting. Some operative systems like macOS ignore hinting at all, and improvements are relevant only at small sizes, so I decided to remove them from my subset.

pyftsubset "src/fonts/Inter-Regular.ttf" --no-hinting --desubroutinize --layout-features=$LAYOUT_FEATURES --unicodes=$UNICODES

The final step is to output these as compressed files optimized for web usage.

# Font files compression

Unless you need to support really old browsers, woff and woff2 formats should be good enough.

If you aren't sure, check compatibility data for compressed file formats.

To export files in these formats you will have to install zopfli and brotli Python libraries and specify the flavor you want to the pyftsubset command.

pyftsubset "src/fonts/Inter-Regular.ttf" --output-file="assets/fonts/Inter-Regular-subset.woff2" --flavor="woff2" --no-hinting --desubroutinize --layout-features=$LAYOUT_FEATURES --unicodes=$UNICODES

After doing this, each font file went from weighing ~100Kb to ~12Kb bringing back the site closer to its original size at ~60Kb per page.

# Performance results

After moving to self-hosted web fonts and applying all these performance adjustments I used webpagetest to run a last performance comparison.

I set the configuration with a Slow 3G network in a Motorola G device using Chrome for Android. The first interesting number was Speed Index, it was slightly faster but by a really small amount to actually make a difference.

That's good! It means my previous font loading strategy was good, and using a different domain for my fonts wasn't affecting content delivery.

Largest Contentful Paint was a metric that improved, as self-hosting your own assets eliminates the need to connect to a new external domain.

When a resource comes from the same domain as the page, the DNS resolution, handshakes, and negotiation have all been made already

For third-party requests using link with preconnect usually allows the browser to run these connections ahead of the resource being requested.

The Google Fonts version of the project had this set, but under certain conditions like a slow network it might not make any difference at all, and browsers might decide to ignore this.

Pre-connecting to third party domains is still a recommended practice, but it's not a silver bullet approach for third-party assets to get faster to the user.

In a way this demonstrates self-hosting resources ends up making a bigger difference for those users under slow connections. If possible, self-hosting always wins across several user conditions like connectivity.

# Wrap-up

I have mentioned this a lot of times in this article, Google Fonts is really fast, and checks all the boxes for a safe and well executed third-party resource.

The benefits of self-hosting font files are still relevant, but only when you match their optimizations like caching strategy, font subsetting and file compression.

You can't afford all these actions on your project? It's fine, Google Fonts is a fair and more than reasonable choice to make.

If you do so, Harry Roberts recently wrote an article on the fastest way to deliver Google Fonts for your site I highly recommend.

Here's a TL;DR list of optimizations and things to remember if you decide to self-host your font files:

• Make sure files are correctly cached by checking their response headers.
• Decide on a set of glyphs and font features, and create a subset file.
• Using modern techniques and tools to compress the final files.
• Measure and compare performance of your new strategy to make sure they represent an improvement to the user experience.

Shout out to Zach Leatherman's article Developing a Robust Font Loading Strategy for CSS-Tricks which was a huge help while applying all these optimizations plus a great inspiration for writing this article.

# Updates

16 AUG 2020 — Initially the article stated the size of the homepage file went down to its original 50Kb weight, but kerning was not included in the subset configuration. That part was updated to reflect the final numbers.