ResourcesFree tools for learning, no sign-up

Watch algorithms run one step at a time. Press play, slow it down, feed in your own numbers, and read the code next to the animation.

Command references grouped by what you are trying to do rather than alphabetically. Accurate, dense enough to keep in a tab.

Small browser tools that do one job properly: encoders, decoders and converters. No sign-up, no upload, and nothing leaves the page.

Write code in your browser and run it in a sandbox: Python, JavaScript, TypeScript, SQL, Bash, C, C++, Go, Rust, Java, C#, Ruby, PHP, Lua, R, Dart and Swift, or a web page with a live HTML, CSS and JS preview. Nothing to install.

Agent skills and MCP servers for Claude Code, Codex, Cursor and VS Code. A short list, each one read before it is listed, with setup for your tool.