Aider describes itself as AI pair programming in your terminal. You run it inside your project directory, describe the change you want, and it edits your files with the model of your choice. It is open source under the Apache 2.0 license.
What sets it apart is how tightly it is tied to git. Aider can commit each change automatically, so every edit lands as its own commit that you can inspect, revert or squash like any other. It also builds a map of your codebase, which is how it copes with projects larger than a single prompt, and it can run linting and tests as part of the loop so a bad edit is caught straight away. Beyond text, you can give it images and web pages as context, and it supports voice-to-code. The site lists support for more than 100 languages, including Python, JavaScript, Rust, Ruby, Go, C++ and PHP.
Model choice is open: the site says it works best with models such as Claude, DeepSeek and OpenAI’s, and with almost any LLM, local models included. That freedom means the price is not Aider’s to set. You pay whichever provider you connect, so cost tracks how much you use it and which model you pick. Installation is two commands: python -m pip install aider-install, then aider-install.
Verdict: a good fit if you already live in the terminal and like git history as your safety net. If you want an agent inside your editor instead, look at Cline, or compare the wider field in the best AI coding tools guide.
Sources: Aider’s website and GitHub repository, checked on September 21, 2026.
