Compiles TypeScript with the real compiler inside the Worker and runs the result in the same sandbox as the JavaScript playground — a disposable Worker with a five-second limit, no DOM and no network unless you allow it. Choose the target and module format, then run the code, emit the JavaScript, or just compile. Types are erased rather than verified: full type checking needs the standard library declarations, which are not bundled, so syntax and emit errors are reported accurately but type mismatches are not.