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User Timing Marks and Measures

Why the audit is important

The User Timing API enables you to measure your app's JavaScript performance. The basic idea is that you decide which parts of your scripts you want to optimize, and then you instrument those parts of your scripts with the User Timing API. From there, you can access the results from JavaScript using the API, or view them on your Chrome DevTools Timeline Recordings.

How to pass the audit

This audit is not structured as a "pass" or "fail" test. It's just an opportunity to discover a useful API that can aid you in measuring your app's performance. The score that Lighthouse reports for this audit corresponds to the number of User Timing Marks and Measures that it finds in your app.

When your app does include User Timing Marks and Measures, you'll see these Marks and Measures in your Lighthouse report.

Check out User Timing API for an introduction on using the User Timing API to measure your app's JavaScript performance.

How the audit is implemented

This section explains how this audit is implemented, so that you can understand how the audit's score is calculated.

Lighthouse extracts User Timing data from Chrome's Trace Event Profiling Tool.