Lighthouse is great. I use it, and I still think it is one of the most useful performance tools available to web developers.
But I wanted something closer to the way I actually debug and ship web products, so I built PerfLens.
PerfLens is a browser-first performance auditing extension that gives you live Core Web Vitals, Lighthouse-style scoring, resource diagnostics, root cause summaries, performance history, and launch evidence directly inside your browser workflow.
Install it here: https://chromewebstore.google.com/detail/perflens/gkogamlpcnneeficmcdcnnnhobnbebdc
Why I Built It
A Lighthouse report is a strong snapshot, but performance work rarely ends with one snapshot.
During real development, I usually want to know:
- What is slowing this page down right now?
- Which resources are heavy?
- Are my Core Web Vitals healthy?
- What should I fix first?
PerfLens is built for that loop.
What It Includes
PerfLens currently supports:
- Core Web Vitals: LCP, FID, CLS, INP, FCP, and TTFB.
- 0-100 performance scoring.
- Resource breakdowns by type and size.
- Audits for oversized images, missing lazy loading, render-blocking scripts, large bundles, weak caching, compression gaps, and heavy CSS.
- Accessibility checks for alt text, language attributes, viewport setup, headings, and form labels.
- Suggestions ranked by impact, effort, and confidence.
- Root cause summaries.
- Framework and build detection.
- Local history per URL.
- Launch evidence packs with desktop/mobile audits, screenshots, videos, JSON reports, prioritized issues, and readiness status.
PerfLens vs Lighthouse
PerfLens is not trying to replace Lighthouse. Lighthouse is still excellent for standardized lab audits.
PerfLens is focused on the browser-side workflow around the audit.
| Lighthouse | PerfLens |
|---|
| One-time baseline report | Live browser-context auditing |
| Standard lab diagnostics | Page-level history and trend signals |
| General recommendations | Suggestions ranked by impact, effort, and confidence |
| Separate report flow | Popup and DevTools workflow |
| Audit categories | Framework/build detection and root cause stories |
| Report export | Launch evidence packs with screenshots, videos, JSON, and readiness status |
For me, the biggest difference is that PerfLens tries to move you from "this is slow" to "this is probably why, and this is what to fix next."
Fix It With AI
When an issue appears on a localhost URL, PerfLens can identify it and generate a focused prompt for Cursor, Claude, Codex, or a custom coding agent. That makes it easier to pass local audit findings directly into your coding workflow.
Final
PerfLens came from a simple idea:
Performance auditing should be closer to the browser, closer to the product, and closer to the next fix.
If you already use Lighthouse, PerfLens can sit next to it as a practical debugging and launch-readiness companion.