DMOJ
Solve archive problems and join contests on an open-source judge
DMOJ is an online judge and contest site. You solve problems from its archive or join contests, and the judge tests your code right away. Contests use several formats, such as ICPC, IOI and AtCoder style, and your results feed into a rating.
Free · Browser · Intermediate
About DMOJ
It trains algorithm skills for contests and olympiads. It has been used to host many contests, including national olympiads, so it suits students preparing for those events and anyone who wants regular contest practice.
The judge supports more than 60 languages. The whole platform is open source under the AGPL license, so schools and clubs can run their own copy.
On Breakpoint since 23 Oct 2026.