Judge0 is a code execution service that takes source code over a simple HTTP API, compiles and runs it inside a locked-down sandbox, and hands back exactly what the program printed, how long it took, and how much memory it used. Send a snippet in any of more than 90 languages, from Python, JavaScript, Rust, and Go to C, Java, and Haskell, and pick the compiler or interpreter variant you need. Each run accepts standard input, command-line arguments, and custom compiler flags, then reports standard output, errors, and a precise verdict covering accepted, wrong answer, time limit, compilation error, or runtime failure. Per-submission controls cap CPU time, memory, stack size, and output file size, so a fork bomb or an infinite loop dies inside its fence instead of disturbing the host. Submissions run one at a time or in batches, and a synchronous mode answers in the same request for snippets that finish fast. Webhooks call your application the moment a long job completes, which keeps polling loops out of worker queues and classrooms alike. Coding platforms grade student work with it, hiring tools run candidate solutions against hidden tests, and AI agents execute the code they generate before trusting it. Official Python and JavaScript SDKs wrap the raw requests, so most integrations shrink to choosing a language and reading the result fields. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. GPL-3.0 licensed.