Report: State of JavaScript 2025_04_01

JavaScript powers the modern web, enabling rich and interactive web applications. In this report we dive into how JavaScript is used on the web, and its adoption and trends both for mobile and desktop experiences.

JavaScript Bytes
JavaScript Requests
JS Evaluation Time
JavaScript Boot-up Time

Lens

Start Date

End Date

JavaScript Bytes

The sum of transfer size kilobytes of all external scripts requested by the page. An external script is identified as a resource with the js or json file extensions or a MIME type containing script or json.

See also: Page Weight

JavaScript Requests

The number of external scripts requested by the page. An external script is identified as a resource with the js or json file extensions or a MIME type containing script or json.

See also: Page Weight

JS Evaluation Time

The number of milliseconds spent evaluating each JavaScript resource.

JavaScript Boot-up Time

The amount of CPU time each script consumes per page. This metric comes from Lighthouse.

See also: Loading Speed