Yellow Lab Tools

Yellow Lab Tools loads a web page in a headless browser and checks whether front-end performance good practices are respected. It detects problems in the HTML, CSS, JavaScript, images and fonts of the page, and gives precise details for each issue found.

Tests can be run on a simulated phone, tablet or desktop. The tool focuses on page weight and front-end code quality rather than on load timings.

Yellow Lab Tools is free and open source under the GPL-2.0 licence. It is available as an online tool on yellowlab.tools, a command-line tool, a Node.js package, a public API and a Docker image for a private instance. The source code has not changed since 2024, but the online tool still works.