User Timing Marks and Measures

What is the User Timing API?

The User Timing API is a way for web developers to measure and understand how web applications are performing within the context of web pages. Since many web applications rely on JavaScript, the User Timing API can pull data that can be used to visualize how scripts are running so they can be optimized accordingly. Web applications can become complex and having an effective way to understand how they are affecting the user experience is key to overall user satisfaction.

How to Use the User Timing API

The User Timing API works by extracting timing data from API calls, which can be used to optimize JavaScript code. If your application utilizes the User Timing API, Lighthouse will identify them within the report. It is not necessarily meant to be a pass or fail, but to see and better understand actual performance, with the associated start time and duration marks. While this provides just a snapshot of performance, to understand how your web applications are performing 24×7, you can set up continuous web application monitoring with Dotcom-Monitor from multiple locations around the world. It is the best way to get alerted if web applications are not functioning as intended or experiencing performance errors, giving teams the ability to remedy them as quickly as possible so to limit impact to future visitors.



Lighthouse is an open-source tool that is used to run an audit against your web pages and provides scores and suggestions for improving page performance, accessibility, SEO, and more.


PageSpeed Terms

PageSpeed Insights is a tool created by Google that reports on the performance of a page on both mobile and desktop devices, and provides suggestions on how that page may be improved.



YSlow is an open-source website analysis tool that can be used to identify web page performance issues. Learn more about the YSlow to enhance your web pages and the user experience.