- codevs: http://codevs.cn/
- 九度OJ: http://ac.jobdu.com/
- hihocoder: http://hihocoder.com/
- SPOJ (Sphere Online Judge): http://www.spoj.com/
- OpenJudge: http://openjudge.cn/
- 猿圈: http://www.oxcoder.com/index.htm
- codechef: https://www.codechef.com/
- topcoder: https://www.topcoder.com/
- LeetCode Online Judge: https://leetcode.com/
- PKU JudgeOnline: http://poj.org/
- http://acm.zju.edu.cn/onlinejudge/
- HDU Online Judge System: http://acm.hdu.edu.cn/
- ACdream Online Judge: http://acdream.info/
- UVa Online Judge: https://uva.onlinejudge.org/
- codeforces: http://codeforces.com/