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AtCoder

atcoder.jp ↗
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AtCoder is a premier competitive programming platform that hosts regular online contests for developers and students of all skill levels. It offers a variety of algorithm and heuristic challenges to help users improve their coding and problem-solving abilities.

  • Weekly competitive programming contests
  • Algorithm and heuristic challenge categories
  • Comprehensive global user ranking system
  • Archive of past contest problems
Who it's for: Best for students, software engineers, and programming enthusiasts looking to sharpen their algorithmic skills through competitive practice. AI

AtCoder provides a structured environment for programmers to test their skills against others globally through timed contests. Participants tackle algorithmic puzzles in categories like the Beginner Contest (ABC) or the Regular Contest (ARC). The platform maintains detailed rankings and a historical archive of problems, making it a valuable tool for both recreational coders and those preparing for technical interviews.

AtCoder manages to balance a high-pressure competitive environment with a genuinely inclusive community spirit. I find the consistent influx of fresh, high-quality problems to be the gold standard for those looking to stretch their algorithmic capabilities. While the interface is utilitarian and occasionally intimidating, it never gets in the way of the core experience. What impresses me most is the platform's commitment to both classic competitive programming and modern heuristic challenges. It is essential reading for anyone serious about mastering technical problem-solving.

Rated and reviewed by Gemini (gemini-3.1-flash-lite) from the page content at scan time — an AI-generated opinion, not a human review.

Pros
  • Highly frequent, well-organized contest schedule
  • Excellent ranking system with global participation
  • Strong focus on both algorithm and heuristic challenges
Cons
  • High difficulty ceiling for newcomers
  • Interface can feel dense for first-time visitors
3 pros 2 cons
AtCoder
atcoder.jp
VS
LeetCode
leetcode.com

Choose AtCoder for pure competitive sport and high-level algorithmic growth, whereas LeetCode is optimized for interview preparation.

Aspect AtCoder LeetCode ↗
Primary Focus Competitive programming contests Technical interview preparation
Problem Style Challenging, creative mathematical puzzles Standard industry interview questions
Community Feel Sports-like rankings and events Professional career and hiring focus
Heuristic Challenges Included as a core category Not a primary focus
Learning Curve Steeper for absolute beginners Accessible with many guided tutorials
Are the contests suitable for beginners?
Yes, AtCoder hosts specific Beginner Contests (ABC) designed for newcomers to competitive programming.
Does the site provide resources for study?
Users can access a deep archive of past problems and utilize the AtCoder Library to practice and study.
  • Contest
  • Ranking: Algorithm
  • Ranking: Heuristic
  • Important announcements
  • Recent announcements
  • AtCoder Regular Contest 222 Announcement
  • CodeQUEEN 2026 -qual- (AtCoder Beginner Contest 462) Announcement
  • AtCoder Beginner Contest 461 Announcement
  • AtCoder Regular Contest++ 221 Announcement
  • AtCoder Beginner Contest 460 Announcement

Section headings detected on the page.

Original title
AtCoder
Original description
AtCoder is a programming contest site for anyone from beginners to experts. We hold weekly programming contests online.
Site
AtCoder
Author
AtCoder Inc.
Reading time
~4 min · 839 words
Mobile-friendly
Yes
Indexable
Yes
jQueryBootstrapGoogle Tag ManagerGoogle Analyticsnginx
Secure (HTTPS)
Yes · HSTS
HTTP status
200 OK
Server
nginx
Page size
7 KB
Load time
706 ms
Scanned
2026-06-13 20:19:40
69
Performance
62
Accessibility
96
Best practices
83
SEO
First Contentful Paint
3.9 s
Poor
Largest Contentful Paint
5.4 s
Poor
Total Blocking Time
51 ms
Good
Visual Stability (CLS)
0.00
Good

Lab data from Google Lighthouse via the PageSpeed Insights API (mobile) · tested Jun 13, 2026. Scores can vary between runs.

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