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What Speed Index means and how to improve it

Speed1 min readFixes check speed-index

Speed Index scores how quickly the visible part of the page fills in. Under 3.4 s is good. It rewards showing content early rather than all at once at the end.

Step by step, with screenshots: How to read a website speed test →

Check your own site

Runs this check and the other 186, free, in about 45 seconds.

What a passing site looks like

  • Speed Index: passesfail · −10 ptseffort M

Speed Index

Why it matters. Speed Index scores how quickly the visible part of the page fills in. A low number means visitors see a complete page early, even if scripts are still loading behind it.

How to fix it.
  1. Prioritise above-the-fold content — critical CSS inline, hero image preloaded, everything else deferred.
  2. Avoid client-side rendering for the first screen; server-render it.

Filed under Speed & Core Web Vitals. Copy is generated from the same catalogue that scores every report, so what you read here is what the report says.