CodinGame - CodinGame provides users with a fun and effective way to learn coding that eschews the rigid structure of traditional teaching methods.

HackerRank - HackerRank is a platform that allows companies to conduct interviews remotely to hire developers and for technical assessment purposes.

CodeCombat - Learn programming with a multiplayer live coding strategy game.

iMocha - Make intelligent talent decisions.

Codility - Codility provides a SaaS platform with advanced validation, security and protection features to evaluate the skills of software engineers.

Codewars - Achieve code mastery through challenge.