Aider is a free, open-source AI pair programming tool that lives in your terminal. One of the pioneers of AI-assisted coding, it has earned more than 49,000 stars on GitHub and remains actively developed, with its latest updates in 2026. Rather than bolting AI onto an editor, Aider works where your code already lives: your existing repository, your shell and your Git history.
You describe what you want in plain language, and Aider edits the right files, explains its changes and commits them to Git with sensible messages. It builds a concise map of your whole repository so the model understands how files relate, supports a wide range of models โ Claude, GPT, Gemini, DeepSeek, local models and more โ and can run tests and linters after each change, fixing errors it introduces. Voice input, image and web-page context, and watch mode round out a tool that feels less like autocomplete and more like a junior engineer you supervise from the command line. The project also maintains a public benchmark leaderboard that measures how accurately each model edits code, which helps users pick the right model for their budget.
Aider is free and open source under the Apache-2.0 license. You only pay for the model access you bring yourself โ an API key from a provider, or nothing at all when using local models.
Aider is for developers who live in the terminal and want AI pair programming without switching editors: solo builders, open-source maintainers and teams who value clean Git history alongside AI speed.