CodePen

Advent of CodeAnnual programming puzzle competition. Runs every December.

Build Your Own XTutorials for rebuilding everything from Git to a database, from scratch.

Can I UseBrowser compatibility tables for every web feature. Essential for developers.

CodecademyInteractive coding lessons for beginners through intermediate developers.

Crafting InterpretersA beloved free book on building your own programming language, by hand.

CS50Harvard's famous intro to computer science. The best free CS course.

CSS Zen GardenThe same HTML, hundreds of different stylesheets. What CSS can do.

CyberChefA Swiss-army knife for encoding, decoding, and data transformation. Built by GCHQ.

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