Run code on your iPhone. Then watch how it ran.

Step tracer

See every line run, and every variable change.

Press Trace instead of Run and the program is recorded as it executes — each line, each call and return, and the value of every variable at that moment. Scrub back and forth or play it like a video, with the current line lit up in the editor. It is what a debugger's stepping does, without the setup.

After any run, the Variables tab lists what the program defined, with type and value. The REPL keeps a session alive between entries. Every saved script is a Shortcuts action.

On-device assistant

An assistant that can actually run your code.

On iPhones with Apple Intelligence, the assistant explains a script, runs it to check the output, traces it to find where a value goes wrong, and proposes a fix you approve before it is applied. It uses Apple's on-device model: no account, no key, and nothing you write leaves the phone.

Code snapshots

Turn a snippet into something worth sharing.

Export any selection as an image — light or dark, with or without line numbers, window controls and the console output underneath. Straight into Messages, a pull request, or your notes.

Import and export real source files through the Files app too, so work you start on the phone doesn't get stuck there.