What it is
Aider is an Apache 2.0 command-line tool that lets you chat with a language model about your code and have it edit the files directly. It builds a map of your whole repository to work in larger projects, works with more than 100 programming languages, and commits each change to git with a descriptive message so you can diff or undo it. It can also lint and test after each edit, take images and web pages as context, and accept voice input.
Aider is free; you pay only for the model API you connect, or nothing with a local model. It suits developers comfortable in a terminal. Its homepage still recommends older models, and releases have slowed, with the latest in February 2026.
Best for
- Developers who live in the terminal and git
- Using cloud or local models with your own API keys
- Keeping every AI change as a separate, undoable commit