- project euler
- a website where you solve math problems with programming
- codewars
- an website with many coding challenges to solve
- Rosetta code
- an wiki with many programming challenges to solve
- edabit
- an website with many coding challenges
- leetcode
- an website with many programming problems to solve
- mit opencourseware
- free courses by the MIT university
- harvard open courses
- free courses by the harvard university
- class central
- a website to search free and paid courses with
- w3schools
- an website to teach html and css
- mdn
- a website by moezilla to teach html and css