Free Developer Tools & Code Editors

The reference material and browser tools that sit alongside the courses. Everything here is free, needs no account, and runs entirely in your browser — nothing to install and nothing to configure before you can use it.

Free online developer tools: code editors for Python, JavaScript and SQL, plus a regex tester, JSON formatter, and coding challenges.

If you are partway through a lesson and need to check a method name, test a regular expression, or run a quick snippet without leaving the site, this is where to come. For structured learning, start with the courses instead; if you are not sure which language to begin with, where to start walks you through choosing one.

Courses by language

Full free courses, language by language: structured lessons with worked examples, practice exercises and a quiz at the end of each one. Lessons in Python, JavaScript, SQL and HTML & CSS also run right in your browser. For a quick syntax refresher instead, the cheat sheets are under Quick Learn.

Learning Tools

Small utilities for the moments a lesson cannot cover: testing a regular expression against your own input, formatting an untidy block of JSON, stepping through a sorting algorithm to see what it does, or working a set of exercises once a topic has clicked.

Inspiration

The questions that come after the syntax: what to build once you can write code, what the job market pays, how to present your work, and how to prepare for a technical interview. Longer reads rather than quick references.

Guides & references