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How I dropped 1s from the First Paint with a smarter font loading strategy

I’ve been learning a lot about measuring performance recently, and I’ve also shared part of this journey on Twitter and Facebook. One thing that I am learning to do more and more, as I wrote about a couple of weeks ago, is measuring before optimizing.

As an exercise, I measured the Time to First Paint for our website on a Moto G on a 3G connection (thanks WebPageTest) which was pretty upsetting.

As I started investigating more on the causes, I’ve found out about two innocent realities that I’ve never considered before about Web Fonts:

  • The cost of using Web Fonts far exceeds the benefits, for our specific use case
  • The First Paint gets delayed by so much if you download your fonts from a different origin that’s served on HTTPS

Reality n.1: The cost of Web Fonts

The website of West Wing Solutions is a pretty simple one. There’s only one font whose only purpose is enhancing the readability of the content, nothing else. It seemed to me at first that readability was a pretty legit reason to be considering a Web Font (specifically, Roboto), until I realized the following:

  • Before rendering your text, browsers wait some — fairly long — time to see if the Web Font can be fetched quickly enough
  • If you are using Google Fonts, and you are @import-ing a CSS file, the browser will have to wait for it before rendering anything

As it turns out, @import-ing files in CSS is a performance anti-pattern since stylesheets are considered by the browser as blocking resources, and the @import-ed one will be requested only after the @import-ing one has finished downloading. As a result, your users end up waiting on two sequential fetches before they can enjoy any of your content. But that's not all.

After the stylesheets are finally ready, your @font-face rule will trigger the actual download of the font file. From this moment on, the browser is going to give it 3 full seconds, before it displays any text. Which brings us to the second realization.

Reality n.2: The cost of a HTTPS-hosted Web Font

Here’s the thing. On a slow connection, HTTPS can delay the actual download of any content (for the first request) for as long as 1 second. Since Web Fonts are usually hosted on a different origin, you will pay this cost twice before rendering anything on screen. Here’s what happens:

  • The user navigates to your site
  • The browser initiates the connection (spending up to 1s if it’s HTTPS)
  • The browser downloads a stylesheet, which itself requires an externally hosted Web Font
  • The browser initiates a second HTTPS connection (up to 1s again)
  • Stylesheets and fonts are finally ready, the browser goes on rendering

Async font is faster font

So how do we stop this madness and improve our First Meaningful Paint by full seconds? Simple, meet your new bible: A Comprehensive Guide To Font Loading Strategies by Zach Leatherman. He suggests a couple of optimized strategies to asynchronously load in fonts. The one I decided to follow (for practicality) goes like the following:

  • First, we tell the browser to render text with a well supported system font (Arial)
  • Then, we asynchronously load in Roboto via this lightweight FontFaceObserver
  • When Roboto is ready, we apply a .fonts-ready** CSS class on the document**, which enables the use of Roboto

And that’s it. What this approach allows us to achieve is an instantaneous rendering of the text, with a visible FOUT (Flash Of Unstyled Text) when Roboto is ready. I’ll be honest, this technique blew my mind for its simplicity. It allowed West Wing Solutions to drop a full second on its First Paint (on 3G).

From this point, I can only see a couple of further improvements that can be considered:

  • A fallback should be provided for when JS is disabled, like a regular tag loading Roboto inside of a
  • A fallback should be put in place for browsers that do not support Promises, which are depended on by the FontFaceObserver. I am not sure whether a polyfill is worth it here, or if we should just give up on the font entirely and stick to Arial.

Crazy Idea: no web fonts?

As I went through the journey of optimizing the Web Fonts loading strategy I started to develop this crazy idea. How bad could it be to actually use a system font for a website that just needs enhanced readability? Since it is so much more lightweight and so impactful on both the First Paint and the First Meaningful Paint, I think we should reconsider the importance of a simple font like Roboto. If you take a look at fontfamily.io, you’ll notice how broadly supported Arial is. It’s pretty darn similar to Roboto, and can be customized through something like ffffallback so that it gets even better. I’m not entirely sold on this yet, but I am starting to think that, sometimes, no font is better than some font.

Isn’t FOUT bad, though?

The strategy I deployed though involves deliberately allowing a FOUT to happen, and that’s something a lot of devs would despise and rather avoid. I believe there is a middle ground where all these ideas can cohexist, so here are two strategies that have come to mind while writing this post:

  • Use Roboto if cached, otherwise use Arial and pre-cache Roboto in the background so that it can be ready for the next navigation
  • Use Roboto if cached, otherwise skip it entirely

Conclusions and self promotion

I’ll close with a side by side video comparison of the before and after. To be honest, I’m still learning. And experimenting. One thing I know I can suggest to you is to keep it simple. Try the technique that works best for you and improve on that, while always applying some good old performance thinking (coining the term right now).

Regardless, I hope you found this helpful!

If you feel this might interest someone else, please leave an heart to help us reach more people! Comments and thoughts are appreciated as well ;)

This article was originally published on the West Wing Solutions blog, a collection of learning material for professionals who are eager to explore the science behind building a successful online product.

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