Aider is an open-source AI pair programming tool that lives in your terminal, enabling developers to collaborate with large language models to build new projects or enhance existing codebases. Unlike cloud-based coding assistants, Aider gives you full control by connecting directly to the LLM provider of your choice — including Claude, GPT-4o, DeepSeek, and local models via Ollama. With over 43,000 GitHub stars and 5.7 million pip installations, Aider has become one of the most trusted AI coding tools in the developer community. Its standout feature is deep codebase awareness: Aider automatically generates a repository map that helps the LLM understand your entire project structure, enabling highly contextual and accurate code edits across multiple files simultaneously. Aider integrates natively with Git, auto-committing every AI-generated change with descriptive messages so you can easily review, diff, and revert modifications. It supports over 100 programming languages and runs linting and tests automatically after making changes. Developers can also use it inside their IDE through watch mode and inline code comments, making it flexible for various workflows. With voice input support and a benchmark-leading performance score, Aider is the go-to terminal AI coding companion for professional developers who value transparency and control.