type --help in the terminal above · unlimited free rule-based
scans (profile → fix → rescan) — just an email, no password, no card
Your profiler found the data. flamelens finds the answer.
Upload a Java Flight Recorder (.jfr) file, a V8
.cpuprofile (Node, Chrome, VS Code), a py-spy speedscope profile, or
a full Chrome DevTools performance trace. Claude reads the hot code, long tasks,
allocation pressure, GC behavior, and contention — and hands back a ranked report
of what's slow, why, and exactly how to fix it, with a downloadable PDF.
Evidence, not vibes
Every finding cites the numbers behind it — sample percentages, pause times, allocation bytes. No invented bottlenecks, and an honest “this profile looks fine” when it does.
Fixes you can apply today
Not “consider optimizing” — the API to switch to, the setting to change, the pattern to apply, with an honest estimate of what it buys you.
Your code stays yours
The raw recording is analyzed and deleted. What we keep is the aggregated summary in your report — method names, never source. Aggregate insights are anonymized to problem-kind and library only.
Plans
Free — unlimited rule-based scans (deterministic checks: hot-spot dominance, GC pressure, contention, thread imbalance; rate-limited to a few an hour), profiles up to 10MB, full reports + PDFs, progress tracked between scans. AI analysis by Claude comes from credit packs or a paid plan. Just verify an email. Students — same, free forever with a school email, with a higher scan rate. Pro ($49/month) — 100 AI scans a month, uploads to 100MB, and live JMX scans: point flamelens at a reachable JVM and it records in place, no file to upload. Enterprise ($99/agent/month) — everything in Pro plus agents that run inside your own network (no inbound port, no exposed JMX) and scheduled sampling for continuous profiling. Create a full account for report history and PRO, or see what the wild is fixing.
Writing, and a game
We publish what profiling real applications turns up — including the time our own tool read five recordings and confidently got them all wrong: read the insights blog.
Or burn some clouds. Cloud Burner is a two-minute toy where you aim the lens and torch the things that actually show up in profiles — the targets are drawn from the same anonymized findings the blog runs on. It is a toy; the real numbers are in your report.
Don't have a profile yet?
The capture guides cover the command line and your IDE — IntelliJ IDEA, WebStorm, PyCharm, and VS Code: how to profile Java with JFR, JavaScript with Node & Chrome DevTools, and Python with py-spy.