Aider

What is Aider?

Aider is a command line tool that pairs you with a large language model to write and edit code. It was created by Paul Gauthier and released in 2023, and it quickly became a favorite among developers who want AI help without leaving the terminal or handing their codebase to a closed editor.

What makes Aider special is how deeply it integrates with git. Before making changes it proposes a plan, then edits the relevant files and creates a commit for you, complete with a descriptive message. You can undo any change, compare what the AI did against your own work, and keep the whole session auditable.

It works with many models, from cloud offerings like GPT, Claude and DeepSeek to local models served by Ollama and other tools. That flexibility means you can use the model you trust most, keep code private by running everything locally, or save money with cheaper models for simple tasks.

Key Features

• Edits multiple files across your whole repository in one request
• Automatic git commits with clear, generated commit messages
• Works with cloud models (GPT, Claude, DeepSeek and more) and local models
• Repo map that helps the model understand your codebase structure
• Voice coding support so you can speak your changes
• Watch mode that responds to file changes automatically
• Scriptable and embeddable, with a Python API
• Lightweight, no vendor lock-in, runs anywhere Python runs

How to get started

Install Aider with pip, set an environment variable with your API key, and you are ready to go. Run it inside a git repository, and it will read your files, build a map of the project, and wait for your instructions.

• Install with pip install aider-chat
• Set your API key, for example export OPENAI_API_KEY=sk-...
• Open a terminal in your git repository
• Run aider and type a change request in plain English
• Review the commit it creates and keep going

Use cases

• Refactoring a function or class across many files
• Writing tests for existing code
• Fixing bugs you can describe but not easily locate
• Explaining unfamiliar code in your own project
• Adding documentation and docstrings
• Migrating code to a new library or framework
• Scripting batch edits with the Python API

Pricing and licensing

Aider itself is free and open source under the Apache 2.0 license, so the tool costs nothing and you can read or fork its source. What you pay for is the underlying model: cloud providers charge per token, while local models are free but need a capable machine to run.

Because there is no subscription to Aider itself, your costs scale with how much you use the AI. Many people run cheap models for routine edits and switch to the strongest models for hard problems.

Pros and cons

Aider's strengths are its simplicity, transparency and model freedom. Everything happens in your terminal and your git history, which makes the workflow easy to audit and undo. It works with almost any model, including private local ones, and there is no vendor subscription.

The trade-offs are that it has no graphical interface, so it will not appeal to people who want a visual editor, and its power depends on the model you connect. Strong reasoning models produce better results, which can mean paying for pricier APIs.

Alternatives

• OpenCode: open-source terminal AI coding agent with a TUI
• Goose: open-source AI agent from Block that runs in the terminal
• Cline: autonomous coding agent inside VS Code
• Continue: open-source AI assistant for VS Code and JetBrains
• Cursor: AI-native graphical editor