CS50 / edX Harvard
freeCanonical CS intro, CS50-issued cert free
7.1M enrollments. Free cert available from CS50 directly (edX verified cert is paid).
| URL | https://cs50.harvard.edu/x |
| Tier | free |
| Relevance | medium |
| Last active signal | CS50x 2026 refresh with AI section |
| Verified alive | yes |
| Category | Learning |