Java performance profiling without the afternoon of squinting
Record a profile, upload it, read an answer. flamelens ranks what is actually costing you time and says what to change.
A JFR recording contains the answer to why your application is slow. Getting it out usually means an hour in a flame graph viewer, working outward from the widest frame and hoping the shape means what you think it means. flamelens reads the recording and writes the report: ranked findings, the evidence behind each one, and a concrete change to make.
Findings, ranked by what they cost
Not a visualisation you have to interpret — a list, worst first.
- Each finding cites the stacks it came from
- Wall-clock and allocation views, not just CPU samples
- A concrete suggested fix, not "consider optimising"
Every profiler you already use
One report format across five recording formats.
- Java Flight Recorder (.jfr)
- V8 .cpuprofile and Chrome DevTools traces
- speedscope and py-spy output
- Native folded and perf stacks
Nothing to install to start
Upload a file from a browser. The agent is for later, if you want it.
- Free tier takes 10MB recordings
- PRO takes 100MB
- Report history, with a downloadable PDF of each
Findings you can hand to someone else
The PDF is the artefact for the ticket, the review, or the postmortem.
- Every finding carries its evidence
- Readable by someone who was not in the debugging session
Frequently asked questions
Do I need to install an agent?
No. Record a profile with the tooling you already have — JFR ships with the JDK — and upload the file. The flamelens agent exists for scheduled and continuous sampling, but nothing about the upload flow requires it.
Does my code get uploaded?
No. A profiler recording contains stack frames — class, method, and line references — not source. flamelens reads the recording you upload and nothing else.
What size recording can I upload?
10MB on the free and student tiers, 100MB on PRO. A few minutes of JFR at the default settings is comfortably inside the free limit.
Is this a replacement for an APM?
No, and it is not trying to be. An APM watches production continuously and tells you when something changed. flamelens takes one recording and tells you why it is slow. They answer different questions, and most teams want both.
Upload a profile. Leave with a plan.
Free to start — 10MB recordings, full reports, no card.
Create a free account