This translation has not been editorially reviewed yet. The German version is authoritative. Deutsche Fassung →
Checking blocking time: when the main thread won't accept input
Total Blocking Time adds up the time during loading when the main thread is so busy it can't accept input. It's measured in the lab, and there it's the most reliable approximation of what users later experience as sluggishness.
- The cause is long, unbroken script execution. Once it's broken into smaller chunks, the browser can respond to input in between — the total work stays the same, but blocking time drops.
- Blocking time is the value that differs most clearly between mobile and desktop: the same work takes many times longer on a phone.
