benchmark
Measures web page performance by collecting real PerformanceAPI data from a running browser session.
Setup & Installation
What This Skill Does
Measures web page performance by collecting real PerformanceAPI data from a running browser session. Captures metric baselines before changes, then compares TTFB, FCP, LCP, bundle sizes, and request counts after. Flags regressions automatically using percentage and absolute thresholds.
Instead of manually comparing Lighthouse screenshots or network tab snapshots across branches, it reads live PerformanceAPI entries, diffs them against a saved baseline, and tells you exactly which metric regressed and by how much.
When to use it
- Capturing a performance baseline before starting a refactor
- Spotting an LCP regression introduced by a new image or layout change on a PR
- Checking JS bundle size growth after adding a third-party dependency
- Comparing total transfer size between the current branch and the main branch
- Running a performance budget check against FCP and JS size limits before merging
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