DMOJ

DMOJ is an open-source platform for programming contests, problem practice, and automated judging. It suits competitive programmers and educational organizations that need contest infrastructure; casual learners seeking a guided course may find its organizer-focused capabilities excessive.

Overview

DMOJ combines an archive of competition problems with public contest hosting and programming autograding. Its archive draws on past CCC, CCO, COCI, IOI, and JOI competitions, among other sources, and the platform runs a Monthly Open Programming Competition. That makes it a useful home for both practice and competitive events rather than a course-led learning product.

The breadth is its defining strength: contest formats, judging behavior, and problem statements can all accommodate demanding programming tasks. That flexibility is most valuable to organizers and serious competitors; learners who want a tightly guided curriculum may prefer a more instructional service.

Key features

Contest formats and judging

Organizers can use ICPC, IOI, AtCoder, or ECOO formats, with system testing, hidden scoreboards, and virtual participation. Interactive and signature-graded tasks, runtime data generators, custom output validators, and per-language resource limits support problems beyond ordinary input-output grading. Scaling to hundreds of judging servers gives large events room to grow, while Stanford MOSS integration adds plagiarism checking. DMOJ also states that AI use is prohibited in rated contests and that judging resources may not be used to train AI.

Problem writing and access controls

Statements support Markdown, LaTeX math and figures, syntax highlighting, PDF generation, and built-in editorials. OAuth login through Google, Facebook, and GitHub, two-factor authentication, and fine-grained staff permissions give organizers useful access controls. DMOJ asks researchers to report potential security issues privately before public disclosure.

Hosting and support

DMOJ provides documentation for installing the site and judge, but its installation guide says the system is tested with MySQL and is unlikely to work with other databases. That is a material constraint for teams with an existing stack built around a different database. Users with contest-hosting questions are directed to contact a moderator.

Pricing

DMOJ is open source and offers public contest hosting for free. That is the straightforward choice for organizers whose contests can be public. Educational organizations can ask about private contest hosting for a small fee; the amount is custom pricing, so it is not possible to budget from a published rate. Self-hosting avoids reliance on public contest hosting but requires installation and the MySQL-compatible setup described above.

Platforms

DMOJ supports web use and lists API, Linux, Windows, and self-hosted platforms. The self-hosted option is especially relevant to organizations wanting to operate their own contest environment, subject to the MySQL requirement.

Who it's for

DMOJ is a strong fit for competitive programmers who want a substantial archive and recurring contests, and for educational organizations that need configurable judging or private contest hosting. It is less suited to learners primarily seeking guided lessons or organizers unwilling to work within its database constraint when self-hosting.

Pros and cons

• Pros: The archive spans several established competitions, and public contest hosting costs nothing.
• Pros: Multiple contest formats, advanced judging options, and MOSS integration give organizers substantial control over assessments.
• Pros: Rich statement tools and fine-grained staff permissions support both problem authors and contest teams.
• Cons: Self-hosting is a poor fit for teams that need a database other than MySQL.
• Cons: Private contest hosting has custom pricing, so educational organizations must inquire before comparing costs.
• Cons: The stated restrictions on AI use in rated contests and on AI training with judging resources rule out those uses.

Alternatives

For a broader browse of services in this category, see Coding Challenge Platforms and Automated Grading Software.

• CodeSignal is worth considering when individuals want practice-based learning, personalized skills paths, and a built-in tutor; its Individuals plan is free.
• CSSBattle is an alternative for readers seeking a free web-based CSS battle format.
• Edabit suits readers who want free web challenges, with all challenges completable at no cost.
• Eolymp is another option for problem databases, educational materials, competitions, and automatic solution testing, with free services and a free trial on its paid offering.
• HackerEarth Assessments may fit teams assessing candidates, with a free tier that includes five test invites, three interview invites, and two admins; unused invites do not carry over.
• AtCoder is a simpler choice for free contest participation and browser-based source-code execution.
• beecrowd may suit educators wanting an individual academic tier with one active subject, up to 20 students, and more than 2,500 programming challenges.
• Codeforces is another free option for open contest participation.

Verdict

Choose DMOJ if you need a free, open-source contest platform with serious judging flexibility, a competition-backed problem archive, and public hosting. Look elsewhere if you need guided instruction, cannot accept the MySQL constraint for self-hosting, or require AI use in rated contests.