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Google Gemini API error

Gemini API 401 authentication: what it means and how to fix it

Error message
401 authentication

Retry? NoLast verified 1 documented fix2 sources

What it means

The API key is missing, invalid, or expired.

Causes

  • Missing API key
  • Invalid or expired API key

How to fix it

  1. Fix 1.

    Verify your API key setup following the API key guide.

More Gemini API errors

All 30 Gemini API errors

HTTP 401 at other providers

Compare 401 across providers

FAQ

What does the Gemini API error "401 authentication" mean?

The API key is missing, invalid, or expired.

How do I fix Gemini API "401 authentication"?

Verify your API key setup following the API key guide.

Should I retry Gemini API "401 authentication"?

No. The official docs treat this error as not retryable: fix the cause before sending the request again.

Which other AI APIs return HTTP 401?

Per their official error docs: Anthropic API (401 authentication_error), Azure OpenAI (401 Unauthorized), Cohere API (401 Unauthorized), DeepSeek API (401 - Authentication Fails), Groq API (401 Unauthorized), Mistral API (401 Unauthorized), OpenAI API (401 Invalid Authentication; 401 Incorrect API key provided; 401 You must be a member of an organization to use the API; 401 IP not authorized), OpenRouter (401 authentication), Vertex AI (401 UNAUTHENTICATED), xAI API (401 Unauthorized).

Sources

Last verified against 2 sources: Gemini API's official docs and official SDK repositories.

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