What it does
Browsertime is a command-line browser measurement engine used to collect web performance data. A developer supplies a page URL or a JavaScript navigation script, selects a browser, and receives timing data and browser artifacts such as JSON and HAR files. It can run from Node.js or a Docker image and supports several desktop browsers, with documented options for real-device mobile testing. The project is open source under Apache License 2.0.
Browsertime is useful when a performance check needs a real browser run rather than a synthetic calculation over source files. Its documentation shows a basic run that loads a URL and writes timing results and a HAR file. For a repeatable comparison, the documented options can run the same URL several times and select a browser; the example below is illustrative and was not executed:
browsertime -b chrome -n 3 https://www.sitespeed.io/
The output can include page-load timings, visual metrics, and recorded video when the required dependencies are installed. A Docker image includes Chrome, Firefox, Xvfb, and the dependencies needed for video and visual metrics; a standalone setup uses Node.js plus installed browsers. The broader sitespeed.io project can build reports from Browsertime results, but this listing is for the measurement engine itself.
The main tradeoff is setup: this is a local CLI, not a hosted browser lab. The docs describe macOS and Linux for standalone use and Windows through Docker. Mobile testing has additional device prerequisites, and the guide says it is not supported in Docker. Confirm browser and metric requirements before making it part of CI.
Strengths
- Runs real browser page loads and produces timing data and HAR artifacts for later analysis.
- The docs describe Chrome, Firefox, Edge, and Safari support, with configurable iterations and browser selection.
- A Docker image bundles browser and video-measurement dependencies for a more repeatable setup.
Watch out for
- A local installation needs Node.js and browser dependencies, or Docker; native Windows use is not documented as supported.
- Mobile testing requires additional device tooling and is not supported in Docker.
Best for
- Comparing web page performance across repeat browser runs or releases
- Collecting browser timing, HAR, or visual-metric artifacts for engineering analysis
- Building a custom performance-testing workflow around a CLI engine
Sources
- Documentation Browsertime 27 (Oct 26, 2026)
- Browsertime Details and Examples (Oct 26, 2026)
- Install Browsertime using npm/yarn or Docker (Oct 26, 2026)
- Browsertime official repository README (Oct 26, 2026)
- Apache License, Version 2.0 (Oct 26, 2026)