Piston-compatible API

Code written for Piston's v2 API runs here with two changes: point its base URL at https://api.onlinecompiler.io/api/v2/piston, and send your API key in the Authorization header. Requests and responses keep Piston's shape, including errors as {"message": "..."}.

curl -X POST https://api.onlinecompiler.io/api/v2/piston/execute \
  -H "Authorization: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "language": "python",
    "version": "*",
    "files": [{ "name": "main.py", "content": "print(input())" }],
    "stdin": "hello"
  }'

Response (200)

{
  "language": "python",
  "version": "3.14",
  "run": {
    "stdout": "hello\n",
    "stderr": "",
    "output": "hello\n",
    "code": 0,
    "signal": null,
    "message": null,
    "status": null,
    "cpu_time": null,
    "wall_time": 21,
    "memory": 9216000
  }
}

Differences from Piston

• Piston's language names and aliases for our 45 languages work, such as py, c++ and csharp. Other languages answer 400 with "runtime is unknown".
• version is accepted and ignored: programs run on the current version that /runtimes lists. run_timeout and run_cpu_time stop the run at the lower of the two, capped at 30 seconds; compiling does not count, and Java, Groovy and F# get a start-up allowance on top (Java (1 s), Groovy (1.5 s) and F# (2.5 s)). Compile limits and memory limits are ignored, and our memory limit applies.
• One file per program, in utf8, base64 or hex. Command-line args are not supported; send input through stdin.
• There is no separate compile stage: compiler errors arrive in run.stderr with a non-zero run.code.
• run.output is stdout followed by stderr, not interleaved. wall_time is in milliseconds and memory in bytes; cpu_time is null.
• run.status is RE for a non-zero exit or too many processes, TO for the 30-second timeout, SG for a signal, OL for an output flood and XX for an internal error.

Moving from Piston's public API? See Piston API alternatives.