Aider is an open source, terminal-based AI coding assistant that integrates with git to make and commit changes to your codebase. It is MIT-licensed, works with any LLM (Anthropic, OpenAI, Groq, local Ollama models), and is built around git as the unit of truth. If you want zero vendor lock-in, full control over which model you use, and a coding assistant that treats git commits as a first-class feature, Aider is worth understanding.
What Aider Is
Aider runs in your terminal. You tell it which files to work in, describe what you want to change, and it edits those files and commits the changes to git automatically. Every change Aider makes is a git commit with a generated message. If you don't like a change, you revert it with git revert like any other commit.
This is a fundamentally different model from Claude Code or Cursor. Those tools have their own internal undo/redo. Aider makes git the undo system, which is both its greatest strength and its biggest learning curve.
How Aider Differs from Claude Code
Claude Code is Anthropic's official agentic coding tool. It is excellent, deeply integrated with Claude's capabilities, and supports sub-agent orchestration for complex tasks. But it is proprietary, only works with Anthropic's API, and costs $100/month for the Max plan (or per-token on the API).
Aider is different in three important ways.
Fully open source (MIT). You can read every line of Aider's code, contribute to it, fork it, or self-host any part of it. There is no vendor relationship beyond the LLM API you choose to use.
Works with any LLM. Aider supports Anthropic Claude (claude-3-5-sonnet, claude-opus), OpenAI GPT-4o, Groq (fast and cheap for simpler tasks), local models via Ollama (llama3, codestral, deepseek-coder), and many others. You pick the model, you pay the API cost directly, and you can switch models mid-project.
Git-native by design. Aider was built around git from the start. Every change is committed. You can run Aider in a feature branch, review its commits with git log, squash them with interactive rebase, and merge normally. This makes Aider feel like a colleague whose work appears in your git history.
Installation
The recommended installation method uses aider-install:
pip install aider-install
aider-install
This installs Aider into an isolated environment and adds it to your PATH. Alternatively, you can install directly with pip install aider-chat, though the isolated install avoids dependency conflicts.
After installing, set your API key:
export ANTHROPIC_API_KEY=your-key-here
# or
export OPENAI_API_KEY=your-key-here
Core Commands and Workflow
Start Aider in your project directory:
aider
Aider opens an interactive session. Key commands:
/add <file> — Add a file to the edit context. Aider only edits files you've explicitly added.
/drop <file> — Remove a file from context.
/diff — Show the diff of the last change before committing.
/undo — Undo the last git commit Aider made.
/git <command> — Run any git command from within Aider.
/model <model-name> — Switch LLM mid-session.
/ask <question> — Ask a question without making changes.
A typical session looks like this:
aider src/auth/login.ts src/auth/types.ts
> Add refresh token support to the login function. Store the refresh token in the database and return it alongside the access token.
Aider reads both files, plans the changes, edits them, and commits with a message like "feat: add refresh token support to login."
Running with Different Models
# Use Claude Opus for complex tasks
aider --model claude-opus-4-5
# Use a local Ollama model (free, private)
aider --model ollama/llama3
# Use Groq for fast, cheap iteration
aider --model groq/llama3-70b-8192
The ability to switch models based on task complexity is genuinely useful. Use a cheap, fast model for simple refactors and a powerful model for architecture changes.
Best Use Cases for Aider
Git-integrated workflows. If your team reviews AI-generated code in PRs and wants that code to appear as real git commits, Aider is the natural fit. The commit history is clean and reviewable.
Open source projects. For maintainers who need to be transparent about how code is generated, Aider's git-first approach means every AI contribution is documented in history.
Teams wanting zero vendor lock-in. If you have a policy against paying Anthropic or OpenAI directly, you can run Aider with a local Ollama model and pay nothing beyond compute.
Multi-model experimentation. Aider makes it easy to benchmark different models on the same coding task by switching with /model.
Privacy-sensitive codebases. Running Aider with a local model via Ollama means your code never leaves your machine.
Honest Weaknesses
Less polished UX than Claude Code. Claude Code's interface, tool use, and sub-agent orchestration are more sophisticated. Aider is a terminal tool that feels like a terminal tool. That's a feature for some developers and a friction point for others.
No built-in sub-agent orchestration. Claude Code can spawn sub-agents to work on parallel tasks. Aider is single-threaded: one conversation, one set of files, one task at a time.
Context window management is manual. You decide which files to /add to context. Claude Code has more sophisticated codebase indexing and automatic context management. With Aider, you can hit context limits if you add too many large files.
Model quality ceiling. If you're running with Ollama on a MacBook, a local llama3 model will not match Claude Opus on complex refactoring. The "bring your own model" flexibility is only as good as the model you bring.
Pricing
Aider itself is free and open source. You pay only for LLM API usage. With Claude claude-3-5-sonnet at Anthropic's current pricing, a typical coding session costs $0.50 to $3.00. With a local Ollama model, it's $0.
This makes Aider genuinely cheaper than any subscription-based tool for developers who don't code with AI constantly.
Keep Reading
- Claude Code Complete Setup Guide — How Aider compares to Anthropic's official agentic tool
- Continue.dev: Open Source Copilot Alternative — Another open source option, IDE-based
- Open Source Alternatives to GitHub Copilot — Full roundup of free and open source AI coding tools
Pristren builds AI-powered software for teams. Zlyqor is our all-in-one workspace — chat, projects, time tracking, AI meeting summaries, and invoicing — in one tool. Try it free.
