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Run, trace, and report JavaScript performance with Chrome
Speedracer executes JavaScript races in Chrome, captures DevTools traces, and generates concise performance reports for regression testing, benchmarking, and analysis.
Speedracer is a CLI tool that runs JavaScript "races" inside Google Chrome, captures low‑level DevTools trace events, and produces both raw .trace.gz files and summarized .speedracer reports. It is designed for developers and performance engineers who need precise metrics on scripting, rendering, and painting phases.
Install globally via npm, write races using the simple race(name, fn) API (ES6 or CommonJS), and invoke to execute them. Chrome (preferably Canary on macOS for headless mode) is driven through the DevTools protocol, and all artifacts are stored in a directory. Use to view a quick summary, or load the trace files into Chrome DevTools for deeper investigation.
speedracer run.speedracerspeedracer displayAdd the tool to your CI pipeline, ensure Chrome is available on the build agents, and script speedracer run as part of performance regression checks. The generated JSON reports can be diffed programmatically, while the trace files can be archived or fed into custom analysis pipelines.
When teams consider Speedracer, these hosted platforms usually appear on the same shortlist.
Looking for a hosted option? These are the services engineering teams benchmark against before choosing open source.
CI regression benchmark
Detect performance regressions between builds by comparing generated reports.
Micro‑benchmarking a rendering algorithm
Capture detailed scripting, rendering, and painting times to optimize the algorithm.
Custom trace analysis
Export .trace.gz files and load them into Chrome DevTools for manual investigation.
Performance education
Teach developers how Chrome’s rendering pipeline works using real trace data.
It drives Google Chrome via the DevTools protocol; headless mode works with Chrome Canary on macOS.
Each race produces a compressed .trace.gz file and a .speedracer JSON report saved in the .speedracer directory.
Speedracer generates summary reports that can be programmatically diffed to identify faster or slower runs.
Races are defined with a simple `race(name, fn)` API using standard ES6 or CommonJS modules.
No built‑in UI; reports are JSON and traces can be opened in Chrome DevTools’ Performance panel.
Project at a glance
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