The short version: real compiler, real hardware, nothing to install. The longer versions are below.
01
A browser IDE for embedded Rust on ESP32. You write no_std Rust in the Playground, a remote build farm compiles it, and the resulting firmware is flashed to the board on your desk over Web Serial. No toolchain, no udev rules, no setup.
02
No. You need a Chromium-based browser (Chrome or Edge — Web Serial is not available in Firefox or Safari), an ESP32 board, and a USB cable. Compilation happens on our build farm, and flashing happens directly from the browser.
03
Six ESP32 targets: the original ESP32, ESP32-C3, ESP32-C6, ESP32-H2, ESP32-S2 and ESP32-S3. Pick the board in the Playground before flashing — the flasher checks that the connected silicon matches and refuses a mismatch rather than writing the wrong image.
04
The median build is 9.4 seconds with a warm cache. Builds are content-addressed: if the exact same sources were already compiled for the same board and toolchain, you get the cached firmware instantly without a rebuild.
05
Free, and no account exists to create — everything works anonymously. There is a fair-use limit of 60 builds per hour per client to keep the farm responsive for everyone.
06
Yes, by default. Saving a sketch gives it an unguessable URL and a secret edit token; nothing lists it anywhere. A sketch appears on the Explore page only if you explicitly publish it, and you can unpublish it again at any time.
07
Flashing only ever writes firmware that matches the code on screen. Editing the source changes its build identity, so the previous binary no longer corresponds to what you see — rebuild first, then flash.
08
The build farm is temporarily unreachable, so new builds are refused rather than queued into the void. Cached builds of unchanged sketches still work. It usually recovers within minutes — try again shortly.
09
No. The ESP32's first-stage bootloader lives in mask ROM and cannot be overwritten, so a failed or interrupted flash is always recoverable by flashing again.
Still curious? The Playground answers most questions faster than prose.