Aider is an open-source AI pair-programming tool that runs directly in a developer's terminal, letting programmers collaborate with large language models (LLMs) to start a new project or work inside an existing codebase. Rather than living inside a proprietary editor or IDE, Aider works as a command-line companion: it reads a project's files, builds a map of the surrounding codebase for context, edits real files on disk, and automatically commits each change to git with a sensible commit message.
Maintainer and background
Aider is developed and maintained by the Aider-AI organization on GitHub, where the project is released under the Apache-2.0 open-source license. The project publishes its own release notes and reports that Aider itself wrote a large majority of the new code shipped in one of its recent releases (88%, according to the project's own figures) — a proof point the team highlights to demonstrate the tool's real-world coding ability. The GitHub repository has accumulated more than 44,000 stars, and the maintainers report roughly 6.8 million total installs and about 15 billion tokens processed weekly, pointing to a large and active open-source user base.
Core features
- Codebase mapping: Aider builds a map of the entire repository so it can work effectively even in large, multi-file projects, not just the file currently open.
- Broad language support: it works with more than 100 programming languages.
- Git-native workflow: every change Aider makes is committed to git automatically with a descriptive message, so edits stay reviewable and reversible.
- Wide LLM support: Aider connects to a long list of providers and models, including Claude (e.g. Claude 3.7 Sonnet), OpenAI models, DeepSeek, Gemini, GROQ, Ollama for local models, Azure OpenAI, and Amazon Bedrock, among others.
- IDE and editor integration: a watch mode lets Aider pick up instructions written as comments inside a normal editor, and a browser-based chat interface is also available for a more visual workflow.
- Multimodal input: Aider can take images and web pages as context and supports voice-to-code dictation.
- Automated linting and testing: it can run linters and test suites after making changes and fix problems it finds.
Pricing and cost model
Aider itself is free and open source — there is no license fee to install or run it. It is not a hosted service, however: using it requires an API key from an LLM provider such as Anthropic, OpenAI, or DeepSeek, and the real cost of using Aider is whatever that provider charges for API usage. Aider also supports connecting to locally run models via Ollama, which can remove per-token API costs for users willing to run their own models. There is no separate Aider subscription or usage fee beyond the underlying model's API cost.
Who it's for
Aider is aimed at developers who prefer working in the terminal and want an AI assistant that operates directly on their real project files and git history, rather than a browser-based or IDE-locked chat assistant. Its codebase mapping and multi-file editing make it well suited to established, larger repositories rather than only small greenfield projects, and its support for many LLM providers, including local models, makes it attractive to teams that want to choose or switch models freely or that need to run models locally for cost or privacy reasons.