- Tokilearning Center (Bahasa Indonesia)
- Ligth Online Judge (English)
- Codeforces (Rusian / English)
- Codechef (India / English)
- Arbiter (Arabic / English)
- URI Online Judge (Portugese / English)
- UVA Online Judge (English)
- USA Computing Olympiad (English)
- University of Science and Technology of China Online Judge (China / English)
- ShareCode ACM Online Judge (English)
- Croatian Open Competition in Informatics [COCI] (English)
- TopCoder (English)
- Sphere Online Judge (English)
- Peking University Online Judge (Japan / English)
- Brilliant (English <bukan online judge, tapi bisa buat belajar competitive programming & melatih algoritma & matematika>)