No. 3 of 30 ·Coding Challenge Platforms

AtCoder

Web

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Freedom report

Two barsScore 6.4

Free tierA free tier is on its own pricing page
Open codeNo open-source code on record
Runs widely1 of 6 device platforms
DocumentedPlans, terms and facts published

AtCoder is ranked #3 of 30 in coding challenge platforms on Freedom251. It runs on Web. There is a free plan.

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: Yes
Primary use: contests
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 IR
Problem library size: 5,000 problems
Solution explanations: Yes

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The record

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

Where it ranks on Freedom251

Best Coding Challenge Platforms in 2026#3 of 30

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Sources

info.atcoder.jp/overview/about/atcoder· checked 1 Oct 2026
info.atcoder.jp/overview/about/services· checked 1 Oct 2026
info.atcoder.jp/overview/contest/intro· checked 1 Oct 2026
info.atcoder.jp/overview/contest/algorithm· checked 1 Oct 2026
atcoder.jp/privacy· checked 1 Oct 2026
atcoder.jp/personal· checked 1 Oct 2026
atcoder.jp/purpose_of_use· checked 1 Oct 2026
atcoder.jp/posts/opt-out-notify-en· checked 1 Oct 2026
atcoder.jp/tos· checked 1 Oct 2026
atcoder.jp· checked 28 Sept 2026
info.atcoder.jp/overview/about/why-tada· checked 1 Oct 2026