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AtCoder
Tokyo, Japan
What it is
AtCoder is a free web service for competitive programming, where users solve problems in contests and can run source code in a browser without setting up a local environment. Its formats include Algorithm Contests and Heuristic Contests. Beginner Contests take place weekly, Regular Contests about monthly, Grand Contests five to six times each year, and heuristic contests about monthly. The practice library contains about 5,000 past problems with explanations, and the service supports a broad range of languages, including C, C++, Python, Rust, Java, and C#. Real-time participation in Algorithm or Heuristic contests affects a user’s AtCoder rating. AtCoder Jobs lets users apply to companies using that rating; PAST is an algorithm skills test available in Japanese and English, with problems updated every six months. The service states that about 200,000 people are registered and about 10,000 participate in real-time contests weekly. It is free to use on the web.
For and against
For
- Free contest participation and browser code execution
- About 5,000 past problems with explanations
- Weekly Beginner Contests and regular contest formats
- Supports a broad range of programming languages
Against
- Terms allow one account per member only
- Account sharing, lending, and transfer are prohibited
The verdict
AtCoder combines scheduled contests with a substantial practice library and browser-based code execution. Its rating, recruiting, and skills-assessment features extend beyond contest participation.
Who it suits
AtCoder suits programmers who want contest practice, a large problem library, and rating-based competition. Its jobs and skills-test offerings may also interest people exploring recruiting or algorithm assessment.
Plans and prices
AtCoder contests
free contest participation · browser-based source-code execution
Read 1 Oct 2026 · info.atcoder.jp
On the record
- Account limit
- The terms allow one account per member and prohibit transferring, lending, or sharing an account.atcoder.jp · read 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 · read 1 Oct 2026
- Analytics integration
- AtCoder uses Google Analytics to measure access trends and improve its website.atcoder.jp · read 1 Oct 2026
- Browser execution
- Users can execute source code in a browser without building a local programming environment.info.atcoder.jp · read 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 · read 1 Oct 2026
- Contest types
- AtCoder offers Algorithm Contest and Heuristic Contest formats.info.atcoder.jp · read 1 Oct 2026
- Practice library
- The service provides about 5,000 past problems and extensive explanations.info.atcoder.jp · read 1 Oct 2026
- Privacy management
- AtCoder says its personal-information protection management system conforms to JIS Q 15001.atcoder.jp · read 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 · read 1 Oct 2026
- Ratings
- Real-time participation in Algorithm or Heuristic contests changes a user's AtCoder rating.info.atcoder.jp · read 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 · read 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 · read 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 · read 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 · read 1 Oct 2026
- What it does
- AtCoder is a competitive-programming contest site where users solve programming problems competitively.info.atcoder.jp · read 1 Oct 2026
