How to profile

Getting the recording is half the job — most teams never profile because the capture step feels arcane. It isn't. Each guide below shows the fastest way to a profile file from the command line and from your IDE, and what to do with it once you have it.

Java · JFR

Java Flight Recorder from the JVM flag, jcmd, IntelliJ IDEA, or VS Code.

JavaScript · Node & Chrome

.cpuprofile from Node, WebStorm, VS Code, or Chrome DevTools' profiler.

Python · py-spy

Sampling a live process with py-spy — no code changes — from any terminal, PyCharm, or VS Code.

C / C++ · perf

Folded stacks from perf, CLion, Instruments, or VTune — Rust and Go binaries too.

C# / .NET · dotnet-trace

EventPipe sampling from the CLI, Rider, or Visual Studio — F# and VB.NET too.

Reading your report

What samples, leaf frames, GC share, and lock convoys mean — a worked example, and what to do about each finding.

Then what? Bring the file to the flamelens terminal: auth <email> → verify <code> → scan init, or upload on the analyze page, where rule-based scans are free and unlimited — profile, fix, and rescan with progress tracked between them. Every format above is analyzed, including full Chrome DevTools traces.