Codewars

freeCodeCamp

freecodecamp.org

Codecademy

codecademy.com

CodeChef

codechef.com

Educative

educative.io

Codeforces

codeforces.com

Codédex

codedex.io

CodeMonkey

codemonkey.com

CodinGame

codingame.com

Code.org

code.org

CodeStudio

codingninjas.com

codedamn

codedamn.com

CodaKid

codakid.com

Edabit

edabit.com

CodeChum

codechum.com

Codementor

codementor.io

CodeCombat

codecombat.com

Codesmith

codesmith.io

Codemia

codemia.io

Codingal

codingal.com

CodingDrills

codingdrills.com

Coderwall

coderwall.com

CodeHS

codehs.com

DataWars

datawars.io

Secure Code Warrior

securecodewarrior.com