How to use Web Speed Test Tool
- Add a Lighthouse JSON report (or paste it) to Web Speed Test Tool to get started.
- Press Read report to run it locally in your browser.
- Read the category scores and Core Web Vitals that Web Speed Test Tool lays out for you.
About this tool
Web Speed Test Tool is a static, client-side tool with no backend. Export a report from Chrome DevTools or PageSpeed Insights and load the JSON into Web Speed Test Tool to see the scores locally.
It shows category scores and Core Web Vitals such as LCP, CLS and TBT, read straight from the JSON. No data is sent anywhere, so it stays fast and private by default.
Frequently asked questions
What does Web Speed Test Tool do?
Use Web Speed Test Tool to check your input without installing anything; everything happens client-side.
Is Web Speed Test Tool free to use?
Yes — Web Speed Test Tool is completely free, with no usage limits.
Does Web Speed Test Tool upload my data?
No — Web Speed Test Tool processes everything locally in your browser, so nothing you enter is uploaded or stored.
What file does Web Speed Test Tool read?
Export a Lighthouse or PageSpeed Insights JSON report and load it into Web Speed Test Tool; it surfaces the scores and Core Web Vitals locally.
Can I use Web Speed Test Tool without a connection?
Yes — after the first load Web Speed Test Tool runs entirely offline.