Andreas AhoniemiHead of Digital, Gullström & Co
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Performance and Core Web Vitals

Performance work means measuring and improving how quickly a page becomes usable for real visitors, expressed in Google’s Core Web Vitals: LCP for when the main content appears, INP for how quickly the page responds to input, and CLS for how much the layout shifts. The work always starts with field data, because lab numbers from a fast machine rarely resemble a phone on a commuter train.

Field data before lab data

A tool score of 95 says little about what visitors experience. The Chrome UX Report and your own in-browser measurement show the actual distribution, and it is the 75th percentile that decides whether you clear the threshold. Sites that look good in the lab and poor in the field almost always have a third-party script problem.

The usual causes

In practice it is four things over and over: images served at full resolution, fonts blocking render, third-party scripts for analytics and chat, and content pushed down when an ad or banner loads. None of them requires a rewrite to fix.

Holding it after launch

Performance that is not monitored disappears within a year, because somebody adds a script. A budget check in the build that fails any change making the page heavier is what makes the improvement durable, and it is a far smaller effort than redoing the work every other year.

Common questions about this service

Do Core Web Vitals really affect rankings?

They are part of Google’s page experience signals, but the effect is small next to content and relevance. The bigger win is commercial: faster pages lose fewer visitors before they have seen anything, and that shows up in bounce rate and conversion far more clearly than in positions.

We already have a caching plugin. Is that not enough?

Caching helps server response time, which is rarely what fails Core Web Vitals. LCP is usually decided by images and fonts, INP by JavaScript blocking the main thread, and CLS by space that was not reserved. None of those is solved by a cache in front of the page.

Start with an hour

Bring a process that grates. We walk it together and you get a straight assessment of whether automating it is worth doing.

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