AtCoder

C tier on Coding Challenge PlatformsScore 6.8 · #5 of 30

Android app: Not listed
Free plan: Yes
Runs on: Web

atcoder.jp

Summary

AtCoder is a free web-based site for competitive programming contests and practice. Users solve problems in Algorithm Contest and Heuristic Contest formats, and can run source code in a browser without setting up a local programming environment. Its practice library contains about 5,000 past problems with explanations, and it supports nearly all major programming languages, including C++, Python, Rust, Java and C#. Beginner Contests run weekly, Regular Contests about monthly, Grand Contests five to six times a year, and heuristic contests about monthly. Taking part in real-time Algorithm or Heuristic contests changes a user’s AtCoder rating. AtCoder Jobs lets users apply to companies using their rating, while PAST is an online algorithm skills test available in Japanese and English, with problems updated every six months. The service says about 200,000 people are registered and about 10,000 users participate in real-time contests weekly. Its terms allow one account per member and prohibit transferring, lending or sharing an account.

Who it is for

AtCoder suits people who want to practice programming problems or compete in browser-based contests. It may also suit users interested in ratings, employer applications through AtCoder Jobs or the PAST skills test.

What is good

Free contest participation
Runs source code in a browser
About 5,000 past problems with explanations
Supports nearly all major programming languages

What to know first

Terms allow only one account per member
Accounts cannot be shared, lent or transferred
PAST problems are updated every six months

Verdict

AtCoder pairs regularly scheduled contests with a large practice library and in-browser code execution. Its rating-linked job applications and skills test add options beyond contest practice, while account sharing is prohibited.

AtCoder plans and pricing

All plans

AtCoder contests Free free contest participation · browser-based source-code execution info.atcoder.jp · 1 Oct 2026

Compared on coding challenge platforms

Free plan: Yesatcoder.jp
Primary use: contestsatcoder.jp
Languages supported: C, C++, C#, Java, Python, Rust, Ruby, Go, Kotlin, Swift, JavaScript, TypeScript, PHP, Perl, Lua, Scala, Haskell, OCaml, Nim, Pascal, R, SQL, Prolog, PowerShell, Bash, Fortran, COBOL, Julia, Dart, Elixir, Erlang, F#, D, Crystal, Clojure, Common Lisp, Scheme, Visual Basic, Lean, LLVM IRatcoder.jp
Problem library size: 5,000 problemsatcoder.jp
Solution explanations: Yesatcoder.jp

Facts

What it does: AtCoder is a competitive-programming contest site where users solve programming problems competitively.info.atcoder.jp · 1 Oct 2026
Contest types: AtCoder offers Algorithm Contest and Heuristic Contest formats.info.atcoder.jp · 1 Oct 2026
Browser execution: Users can execute source code in a browser without building a local programming environment.info.atcoder.jp · 1 Oct 2026
Contest schedule: Beginner Contests run weekly, Regular Contests about monthly, Grand Contests five to six times yearly, and heuristic contests about monthly.info.atcoder.jp · 1 Oct 2026
Scale: AtCoder states that about 200,000 people are registered and about 10,000 users participate in real-time contests weekly.info.atcoder.jp · 1 Oct 2026
Practice library: The service provides about 5,000 past problems and extensive explanations.info.atcoder.jp · 1 Oct 2026
Programming languages: Commonly used languages include C++, Python, Rust, Java, and C#; AtCoder supports nearly all major programming languages.info.atcoder.jp · 1 Oct 2026
Ratings: Real-time participation in Algorithm or Heuristic contests changes a user's AtCoder rating.info.atcoder.jp · 1 Oct 2026
Recruiting integration: AtCoder Jobs lets users apply to companies using their AtCoder rating, including for new graduate, experienced, part-time, and internship roles.info.atcoder.jp · 1 Oct 2026
Skill assessment: PAST is an online algorithm skills test available in Japanese and English, with problems updated every six months.info.atcoder.jp · 1 Oct 2026
Analytics integration: AtCoder uses Google Analytics to measure access trends and improve its website.atcoder.jp · 1 Oct 2026
Privacy management: AtCoder says its personal-information protection management system conforms to JIS Q 15001.atcoder.jp · 1 Oct 2026
Third-party disclosure: AtCoder says it does not provide personal information to third parties without user consent except where required by law.atcoder.jp · 1 Oct 2026
AI-training opt-out: Users can opt out globally or per submission from licensing submitted source code to AI companies for training data.atcoder.jp · 1 Oct 2026
Account limit: The terms allow one account per member and prohibit transferring, lending, or sharing an account.atcoder.jp · 1 Oct 2026