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AtCoder

atcoder.jp

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Spec score 8.1 #8 of 30 in Coding Challenge Platforms

What it is

AtCoder is a free web service for competitive programming contests and practice. Users solve programming problems in Algorithm Contest and Heuristic Contest formats, and can run source code in a browser rather than 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 take place weekly, Regular Contests about monthly, Grand Contests five to six times a year, and heuristic contests about monthly. Real-time participation in Algorithm or Heuristic contests changes a user's AtCoder rating. AtCoder Jobs lets users apply to companies using their rating for roles including internships and experienced positions. PAST is an online algorithm skills test available in Japanese and English, with problems updated every six months. AtCoder says it has about 200,000 registered users and about 10,000 participants in real-time contests weekly. Its terms limit members to one account and prohibit account sharing, lending, or transfer.

Spec sheet

What it does
AtCoder is a competitive-programming contest site where users solve programming problems competitively.Read 1 Oct 2026 · info.atcoder.jp
Headquarters
Tokyo, JapanRead 28 Sep 2026 · atcoder.jp
Founded
2012Read 28 Sep 2026 · atcoder.jp
Account limit
The terms allow one account per member and prohibit transferring, lending, or sharing an account.Read 1 Oct 2026 · atcoder.jp
AI-training opt-out
Users can opt out globally or per submission from licensing submitted source code to AI companies for training data.Read 1 Oct 2026 · atcoder.jp
Analytics integration
AtCoder uses Google Analytics to measure access trends and improve its website.Read 1 Oct 2026 · atcoder.jp
Browser execution
Users can execute source code in a browser without building a local programming environment.Read 1 Oct 2026 · info.atcoder.jp
Contest schedule
Beginner Contests run weekly, Regular Contests about monthly, Grand Contests five to six times yearly, and heuristic contests about monthly.Read 1 Oct 2026 · info.atcoder.jp
Contest types
AtCoder offers Algorithm Contest and Heuristic Contest formats.Read 1 Oct 2026 · info.atcoder.jp
Practice library
The service provides about 5,000 past problems and extensive explanations.Read 1 Oct 2026 · info.atcoder.jp
Privacy management
AtCoder says its personal-information protection management system conforms to JIS Q 15001.Read 1 Oct 2026 · atcoder.jp
Programming languages
Commonly used languages include C++, Python, Rust, Java, and C#; AtCoder supports nearly all major programming languages.Read 1 Oct 2026 · info.atcoder.jp
Ratings
Real-time participation in Algorithm or Heuristic contests changes a user's AtCoder rating.Read 1 Oct 2026 · info.atcoder.jp
Recruiting integration
AtCoder Jobs lets users apply to companies using their AtCoder rating, including for new graduate, experienced, part-time, and internship roles.Read 1 Oct 2026 · info.atcoder.jp
Scale
AtCoder states that about 200,000 people are registered and about 10,000 users participate in real-time contests weekly.Read 1 Oct 2026 · info.atcoder.jp
Skill assessment
PAST is an online algorithm skills test available in Japanese and English, with problems updated every six months.Read 1 Oct 2026 · info.atcoder.jp
Third-party disclosure
AtCoder says it does not provide personal information to third parties without user consent except where required by law.Read 1 Oct 2026 · atcoder.jp

Plans and prices

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

Every AtCoder plan and price →

Strong points and limits

Strong points

  • Free contest participation
  • Run code in a browser
  • About 5,000 practice problems with explanations
  • Supports a wide range of programming languages
  • Contest participation updates AtCoder rating

Limits

  • One account per member
  • Accounts cannot be shared, lent, or transferred

Who it suits

AtCoder suits people who want programming contests, browser-based coding, or a substantial problem library for practice. It may also suit job applicants who want to apply using an AtCoder rating.

Verdict

AtCoder combines recurring contests, browser-based execution, and a large practice library at no charge. Its rating also connects to AtCoder Jobs, while account use is restricted to one account per member.

Where Specifiction places it

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