DMOJ

Overview

DMOJ pairs a competition-problem archive with contest hosting, automated judging, and tools for writing problem statements. It is most compelling for serious programming practice and for organizers who want control over contest formats and grading.

Its breadth favors competitive programming over guided instruction: learners seeking a structured course may find a contest platform less suited to their needs.

Key features

Problem archive and contests

The archive includes problems from past CCC, CCO, COCI, IOI, and JOI competitions, alongside material from other sources. DMOJ also runs a Monthly Open Programming Competition, giving participants a recurring public event on the same platform they can use for practice.

Configurable judging

DMOJ supports ICPC, IOI, AtCoder, and ECOO contest formats, plus system testing, hidden scoreboards, and virtual participation. Interactive and signature-graded tasks, runtime data generators, custom output validators, and per-language resource limits give organizers ways to handle problems that go beyond standard input-output grading. Judging can scale to hundreds of servers, and Stanford MOSS integration supports plagiarism checking.

Statements and access controls

Problem statements can use Markdown, LaTeX math and figures, syntax highlighting, PDF generation, and built-in editorials. OAuth login through Google, Facebook, or GitHub, two-factor authentication, and fine-grained staff permissions give contest operators options for account access and administration.

Hosting and restrictions

DMOJ provides installation documentation for both the site and judge. Its installation guide says the site is tested with MySQL and is unlikely to work with other databases, a meaningful constraint for teams with a different database environment. Educational organizations can contact DMOJ about private contest hosting for a small fee. AI use is prohibited in rated contests, and DMOJ prohibits using its judging resources to train AI.

Pricing

DMOJ is open source and offers free public contest hosting. The Public contest hosting plan costs nothing and covers public contests hosted on DMOJ, making it the straightforward choice for organizers whose events can be public. Educational organizations can ask about Private contest hosting for a small fee; its price is custom pricing, so it is not a published-cost alternative to public hosting.

Platforms

DMOJ lists API, Linux, self-hosted, web, and Windows support. The self-hosting option is useful to organizations that want to install the site and judge themselves, but the MySQL guidance may rule it out for teams committed to another database.

Who it's for

DMOJ fits competitive programmers who want a substantial archive and recurring contests, and organizers who need multiple contest formats, configurable judging, and rich problem statements. Its free public hosting lowers the barrier for open events. Organizations that need private contests can inquire about the small-fee option, while teams seeking a guided learning path or database flexibility beyond MySQL should consider a different fit.

Pros and cons

• Pros: A broad archive spanning major competition sources gives serious programmers plenty of contest-oriented practice.
• Pros: Multiple formats and advanced judging features support organizers with varied scoring and problem requirements.
• Pros: Free public contest hosting and open-source self-hosting offer two ways to use the platform.
• Cons: The installation guide warns that the site is unlikely to work with databases other than MySQL, limiting self-hosting flexibility.
• Cons: Private hosting is available only through an inquiry and a small fee, rather than a stated price.
• Cons: Rated contests prohibit AI use, and judging resources cannot be used for AI training.

Alternatives

For a broader set of Coding Challenge Platforms or Automated Grading Software, compare the relevant category lists.

• CodeSignal is a better fit for individuals who want practice-based learning, personalized skills paths, bite-sized modules, and a skills profile in its free plan.
• HackerEarth Assessments may suit teams focused on assessment invites: its free plan includes five test invites, three interview invites, and two admins, with unused invites not carrying over.
• AtCoder is a simpler choice for free contest participation and browser-based source-code execution.
• beecrowd may suit an individual educator who needs one active subject, up to 20 students, and access to 2,500+ programming challenges on its Academic Free plan.
• Codeforces is an alternative when free, open contest participation is the priority.
• CodingBat is a simpler option for free Java and Python browser-based problem practice, with an account optional.
• CSSBattle is an alternative for free-to-play daily CSS challenges.
• Edabit is worth considering when the priority is completing challenges for free.

Verdict

Choose DMOJ if you are a competitive programmer or contest organizer who values a deep problem archive, free public hosting, and flexible judging. Its strongest case is the range of contest and grading tools in an open-source platform; look elsewhere if you need a guided learning product or self-hosting that is likely to work with a database other than MySQL.