Fidinpamp

March 26th, 2024

If you’re a fan of gratuitous initialisms, you’ll love Google’s core web vitals. Just get a load of the obfuscation in the important-sounding metrics like CLS, FCP, LCP, and more.

To be fair to Google, this is a problem in the web performance world in general. Practioners prefer to talk about TTFB rather than “time to first byte” even though both contain exactly the same number of syllables.

The big news in the web performance community this month is the arrival of a new initialism. INP sounds like one of those pseudo-scientific psychologic profiles but it’s meant to stand for Interaction to Next Paint (even if they were to swear off pointless initialisms, you’d still have to pry Pointless Capitalisation from Google’s cold dead hands).

This new metric is a welcome one. It’s replacing first input delay. Sorry, First Input Delay, or FID, one of the few web vital initialisms that can be spoken as a word, making it a true acronym (fortunately fid’s successor, inp, also works as an acronym).

First Input Delay has long outstayed its welcome. It was always an outlier in the core web vitals. It didn’t seem to measure anything actually useful. I know it sounds like it’s measuring the delay until the user can interact with a web page, but when you dive into what it actually does, it’s a mess:

FID measures the time from when a user first interacts with a page (that is, when they click a link, tap on a button, or use a custom, JavaScript-powered control) to the time when the browser is actually able to begin processing event handlers in response to that interaction.

See that word “begin” in there? It’s doing a lot of work. First Input Delay doesn’t measure the lag between the user interaction and the browser response; it only measures the lag between the user interaction and the browser beginning to respond. The actual response could take ages, but that lag doesn’t get measured. Unlike the other core web vitals, this metric is very far removed from what actually matters to the user’s experience.

What the fid where they thinking? How the fid did this measurement ever get included in core web vitals in the first place?

Well, feel free to take what I’m about to say as pure gossip, but I have my sources, I trust ’em, and no, I’m not going to reveal ’em…

It’s because of AMP.

Remember Google AMP? An acronym so pointless they eventually just forgot it ever stood for anything?

The AMP project ended up doing incredible damage to Google’s developer relations. By colluding with the search team to privilege the appearance of AMP pages in the top news carousel, Google effectively blackmailed the entire publishing industry into using their format.

In the end, it didn’t work. It was a shit format. All they did was foster resentment and animosity:

AMP seems to have faded away. Most publishers have started dropping support, and even Google doesn’t seem to care much anymore.

It turns out that Google search wasn’t the only team infected by AMP. The core web vitals team also had to play ball.

Originally they had a genuinely useful metric for measuring the lag between input and response. But guess which pages did terribly? That’s right: AMP pages.

Rather than ship an actually-useful measurement, the core web vitals team instead had to include the broken First Input Delay, brainchild of a certain someone on the AMP team.

Now it all makes sense.

So good riddance to FID. Welcome to INP. And here’s hoping it won’t be much longer till we’re finally burying AMP.