Judge0

Overview

Judge0 is an open-source online code execution system created by Herman Zvonimir Došilović (established August 2016) and run by Judge0 d.o.o. in Zagreb, Croatia. It is an HTTP JSON API: you POST a submission with language_id, source_code and optional stdin, receive a token, and poll for stdout, stderr, exit code, CPU time and memory, or supply a callback_url to be notified. It comes in two flavours, Judge0 CE and Judge0 Extra CE, which differ in the supported languages (the homepage says 60+, the README 90+). Each submission is compiled and run inside an isolate sandbox, which the isolate project describes as using Linux namespaces and control groups; the service itself is deployed as Docker Compose services (API, workers, PostgreSQL, Redis) and the changelog says it has only been tested on Linux.

There is no state between calls: every submission is a fresh run bounded by cpu_time_limit (default 2 s, maximum 15 s), wall_time_limit (default 5 s, maximum 20 s), memory_limit (default 128,000 KB, maximum 256,000 KB), max_file_size and max_processes_and_or_threads, all of which an administrator can raise on a self-hosted instance. Network access is governed by the enable_network flag added in v1.13.0. The hosted service is sold through RapidAPI (CE and Extra CE listings, Basic plan at $0) and directly from judge0.com in EUR tiers; the GitHub README positions it "for humans and AI" and lists AI agents first among use cases. The code is GPL-3.0; official Python (pip install judge0, MIT) and JavaScript SDKs cover RapidAPI, AllThingsDev and self-hosted endpoints. The latest tagged release is v1.13.1 (18 April 2024), which fixed three CVEs; the repository was still receiving commits in October 2026.

Notable

• Established August 2016; the design is described in the MIPRO 2020 paper "Robust and Scalable Online Code Execution System"
• Latest release v1.13.1 (18 April 2024) fixed CVE-2024-28185, CVE-2024-28189 and CVE-2024-29021; versions before 1.13.0 receive no security support
• About 4.5k GitHub stars; the README cites dozens of academic papers that use Judge0

Judge0 specifications

Facts from Judge0’s public documentation, verified November 9, 2026. Performance numbers are vendor claims.

Strengths and trade-offs

Strengths

• You want a mature, widely integrated submit-and-poll judge with explicit CPU, wall-clock, memory and file-size limits per run
• You need 60-90+ languages, including compiled ones, behind one JSON API
• You run on-premise and want a GPL-3.0 stack you can deploy with Docker Compose
• You are building batch evaluation and want batched submissions and webhooks rather than long-lived sessions

Trade-offs

• Stateless by design: no filesystem or process survives between submissions, so multi-step agent work must re-send everything each time
• Documented defaults cap a run at 5 s wall time (20 s maximum) and 256 MB on the hosted configuration
• isolate is a process-level sandbox (namespaces and cgroups), not a VM; the self-host guide for Ubuntu 22.04 requires disabling the unified cgroup v2 hierarchy
• GPL-3.0 licence and the last tagged release dating from April 2024; no compliance certifications are published

Good fit for: Batch "submit code, get stdout" judging in 60-90+ languages with per-submission CPU, wall-clock and memory limits.

Use cases Judge0 fits

• Code interpreters: Open-source submit-and-run API in 60 to 90+ languages with per-submission CPU, wall-clock and memory limits; hosted or self-hosted.

How Judge0 compares

See all Judge0 alternatives →

Frequently asked questions

Sources

1. judge0.com
2. github.com/judge0/judge0
3. ce.judge0.com
4. github.com/judge0/judge0/blob/master/CHANGELOG.md
5. github.com/judge0/judge0/blob/master/SECURITY.md
6. github.com/judge0/judge0-python
7. github.com/judge0/examples
8. github.com/ioi/isolate
9. rapidapi.com/judge0-official/api/judge0-ce/pricing