# How to minimise main-thread work

> Parsing, compiling and running JavaScript, plus styling and layout, all happen on one thread. Less script and simpler CSS keep it free for interaction.

Speed & Core Web Vitals · HTML version: https://getreport.app/learn/main-thread-work

## Main-thread work

Passing looks like: Main-thread work passes.

**Why it matters.** This is the total time the browser spent parsing, compiling and running your page's code. While it works, it cannot respond to the visitor.

**How to fix it.**

1. Reduce JavaScript first — it dominates this number on almost every site.
2. Cut style and layout work by simplifying CSS selectors and DOM size.

Check your own page: https://getreport.app/