What is a Speedindex?

Calibre records a metric called "Speedindex". Coined by Webpagetest.com, speedindex is a method of calculating a score that indicates the time it took your page to become visually complete.

Speedindex is captured by recording a video of your page as it loads, which is then broken down into a series of screenshots (every 100ms) — These screenshots are analysed against the final frame of the video until the point where "visual completeness" is reached.

The lower the speedindex, the better. — Here's a rough guide to get you started.

A speed index of:

  • 1000 or less is excellent
  • 2000 or less is good
  • 3000 — 5000 means you need some improvement
  • > 5000 means that you have some serious work ahead

To read more about how Speedindex works, please see the webpagetest documentation

Because speedindex is an abstract number applied to a user timing it can be difficult for all members of a team to grasp. At Calibre we instead recommend discussing other easy to understand User Focused Metrics.