aider/aider/website/_includes/special-keys.md

Aider has special support for providing OpenAI and Anthropic API keys via dedicated command line switches --openai-api-key and --anthropic-api-key.

You can also set those API keys via special entries in the yaml config file, like this:

openai-api-key: <key>
anthropic-api-key: <key>

All other LLM providers can use one of the following methods to set their keys:

API keys on the command line

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Use --api-key provider=<key> which has the effect of setting the environment variable PROVIDER_API_KEY=<key>. So --api-key gemini=xxx would set GEMINI_API_KEY=xxx.

API keys in a .env file

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The .env file is a great place to set API keys and other provider API environment variables:

GEMINI_API_KEY=foo
OPENROUTER_API_KEY=bar
DEEPSEEK_API_KEY=baz

API keys in .aider.conf.yml

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Or you can set API keys in the .aider.conf.yml file via the api-key entry:

api-key:
- gemini=foo      # Sets env var GEMINI_API_KEY=foo
- openrouter=bar  # Sets env var OPENROUTER_API_KEY=bar
- deepseek=baz    # Sets env var DEEPSEEK_API_KEY=baz