How to install Aider, step by step

Aider is a free, open-source AI pair programmer that lives in your terminal and edits files directly in your git repo. Every change becomes a commit, so nothing the AI does is lost or hidden. This guide takes you from zero to your first AI-assisted edit in about ten minutes.

What you'll end up with: Aider running in your terminal, connected to a model (DeepSeek for near-free costs, or Claude for top quality), editing a real project.

Before you start

You need three things. Don't worry if you're missing some — we cover each below.

A terminal. Terminal on macOS/Linux, or PowerShell on Windows.
Python 3.8 or newer. Check with python --version.
A git repository. Aider works on top of git. Any project folder that's a git repo works.

Step 1 — Check that Python is installed

Open your terminal and run:

python --version

If you see something like Python 3.11.4, you're set. If you get an error or a version below 3.8, install a current Python from python.org (Windows/macOS) or your package manager (brew install python on macOS, sudo apt install python3on Ubuntu). On some systems the command is python3 instead of python.

Step 2 — Install Aider

The maintainers recommend a dedicated installer that keeps Aider isolated from your other Python packages, so it can't break them. Run:

python -m pip install aider-install
aider-install

This installs Aider in its own environment and adds the aider command to your path. When it finishes, confirm it worked:

aider --version

You should see a version number print out.

If aider isn't found after installing, close and reopen your terminal so it picks up the updated path. On Windows, use a fresh PowerShell window.

Step 3 — Choose a model and get an API key

Aider needs a model to think with. You bring your own API key, which is why Aider itself is free — you pay only the model provider, and only for what you use. Two popular choices:

Option A — DeepSeek (cheapest)

DeepSeek's coding models are strong and extremely cheap, often a few dollars a month for regular use. Create an account at DeepSeek's platform, add a small amount of credit, and generate an API key from their dashboard.

Option B — Claude (highest quality)

Anthropic's Claude models lead on complex, multi-file work. Costs are higher than DeepSeek but you pay per use. Create a key in the Anthropic console.

Keep your key secret. An API key is like a password that can spend your money. Never paste it into a website, commit it to git, or share it in a screenshot.

Step 4 — Give Aider your key

Set your key as an environment variable so Aider can read it. Replaceyour-key-here with your actual key.

DeepSeek

macOS / Linux:

export DEEPSEEK_API_KEY=your-key-here

Windows PowerShell:

$env:DEEPSEEK_API_KEY="your-key-here"

Claude (Anthropic)

macOS / Linux:

export ANTHROPIC_API_KEY=your-key-here

Windows PowerShell:

$env:ANTHROPIC_API_KEY="your-key-here"

This sets the key for the current terminal session only. To make it permanent, add theexport line to your shell profile (~/.zshrc or ~/.bashrc), or store it in an .env file that Aider reads automatically.

Step 5 — Start Aider in your project

Move into a project folder that's a git repo. If it isn't one yet:

cd my-project
git init

Now launch Aider, telling it which model to use.

With DeepSeek:

aider --model deepseek

With Claude:

aider --model sonnet

Aider starts a chat prompt right in your terminal. It already sees your repo.

Step 6 — Make your first edit

Add the files you want Aider to work on, then just describe the change in plain language.

/add index.html
> Add a dark mode toggle button in the top-right corner

Aider proposes the edit, applies it to the file, and commits it to git with a clear message. Because every change is a commit, you can review it with git diff or undo it withgit revert if you don't like it.

Handy commands inside Aider:/add a file to the chat, /drop to remove one,/undo to reverse the last change, /diff to see what changed, and/help for the full list.

Common problems

"Command not found: aider"

Reopen your terminal, or check that the install step finished without errors.

Authentication or 401 errors

Your key isn't set in this terminal session. Re-run the export command, and make sure you copied the whole key with no trailing spaces.

Aider won't edit a file

Add it to the chat first with /add filename. Aider only edits files it's been given.

Is Aider right for you?

Aider is a fantastic fit if you're comfortable in a terminal and want maximum control at minimum cost — especially paired with DeepSeek. If you'd rather work in a visual editor or skip the setup entirely, other tools may suit you better.

Not sure Aider is your best match?

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