Web Performance Calendar

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The Web Performance Calendar just started up again this year. The first two posts so far are about, well, performance! First up, Rick Viscomi writes about the mythical “fast” web page:

How you approach measuring a web page’s performance can tell you whether it’s built for speed or whether it feels fast. We call them lab and field tools. Lab tools are the microscopes that inspect a page for all possible points of friction. Field tools are the binoculars that give you an overview of how users are experiencing the page.

This to me suggests that field tools are the future of performance monitoring. But Rick’s post goes into a lot more depth beyond that.

Secondly, Matt Hobbs wrote about the font-display CSS property and how it affects the performance of our sites:

If you’re purely talking about perceived performance and connection speed isn’t an issue then I’d say font-display: swap is best. When used, this setting renders the fallback font almost instantly. Allowing a user to start reading page content while the webfont continues to load in the background. Once loaded the font is swapped in accordingly. On a fast, stable connection this usually happens very quickly.

My recommendation here would be to care deeply about the layout shift if you use this property. Once the font loads and is swapped out you could create a big shift of text moving all about over the place. I once shipped a change to a site with this property without minding the layout shift and users complained a lot.

It was a good lesson learned: folks sure care about performance even if they don’t say that out loud. They care deeply about “cumulative layout shift” too.

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