The Playground records small, self-contained programs in a cloud sandbox — no Docker, no CLI, no account required.
Pick a language (Rust, C, C++, Go) and write a main.
Hit Run. We compile it and record it under rr on a single-use
Fly.io machine with real hardware perf counters.
The trace streams into the view live as it's extracted.
The sandbox is deliberately constrained:
std-only — no third-party packages / crates
no network
2 GB RAM, 2 CPUs, and a wall-clock time limit
one source file (a main)
Need dependencies, multiple files, or your real project? Use the rion CLI instead — it records whatever you can build.
| Playground | rion CLI | |
|---|---|---|
| Setup | none | Docker + npx |
| Where it runs | cloud sandbox | your machine |
| Your code | one std-only file | any project you can build |
| Account | not required | required (attributed to you) |
| Recorder | mainline rr (real PMU) | rr.soft (software counters) |