What does the Speed Index measure

The Speed Index measures how fast the content is displayed while the page is loading.

A page that starts displaying elements after one second and loads in 5s will have a better Speed Index score than the same page that displays elements after 4s and loads in 5s.

The Speed Index is expressed in seconds but it is a score. It is not placed in a timeline, and does not correspond to a specific event at a given moment.

How to improve the Speed Index

Anything you do to improve the loading speed should improve the Speed Index.

Apart from that, 2 other elements have a strong impact on the Speed Index:

The TTFB

TTFB (”Time To First Byte”)

By reducing the waiting time for the first byte, you bring the time when items are displayed closer together.

Javascript and "secondary" loads

You should work on:

• Reduce the execution time of Javascript
• Reduce the work for the browser to display the page (complexity, CSS classes, etc.)

Rating

The rating for this indicator is: