Skip to content
Permo Docs

Benchmark index (CPU/Memory Power)

The benchmark index is a rough measure of how fast Google’s test computer was. During the test, Lighthouse runs a short standard calculation and records how quickly the machine got through it. Lighthouse reports it as “CPU/Memory Power”.

Why it matters

Section titled “Why it matters”

It’s about Google’s test machine, not about your site and not about your server. It helps when two tests of the same page come out differently: if the benchmark index was clearly lower in one of them, the test computer was slower or busier, and the metrics that depend on processing power, such as Total Blocking Time, suffer.

Results are best compared when the benchmark index is similar. A change in the metrics with a similar benchmark index points to a change in the page.

What influences it

Section titled “What influences it”

Browser: The processor of the machine running the test, and how much other work it has at that moment. Google’s test machines differ, and so does their load, so the value varies from test to test. Changes in Chrome and Lighthouse can change how the index is calculated; values from different versions aren’t directly comparable.

Your site has no influence on it.

In Permo

Section titled “In Permo”

Permo shows the benchmark index on its PageSpeed page under Test machine, next to the details of the test environment. It describes Google’s test computer, not your own server.

Section titled “Related”

Sources