There are several free sites to practice your coding skills and improve your preparation for a technical interview. Here you have some of the most useful:
Codewars offers a fun way to learn coding. With a martial-arts theme, the program is based on challenges called “kata.” Complete them to earn honor and progress to higher ranks.
Codecademy is where most people who are new to coding get their start. If you haven’t been to the site yet…where have you been!? The platform revolves around interactive learning; that is, you read a little, type you code right into the browser, and see results immediately.
Free Code Camp
Teaches coding first through an established curriculum (approx. 800 hours total), then by giving you hands-on experience working on projects for nonprofits.
General Assembly’s free online learning platform. Entirely project-based. You build a “project” with each walk-through.
Competition to get into MIT may be stiff, but accessing their course material has no minimum SAT score. They maintain an online library of every subject they teach, with no account required for access.
The Odin Project
Made by the creators of Viking Code School—a premiere online coding bootcamp. The Odin Project is their free version.