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API Keys

All requests to ModelStack require authentication via an API key. Keys are passed in the Authorization header using the Bearer token format.

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Header Format

Authorization: Bearer [your_api_key]

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Key Format

ModelStack API keys follow this format: 
sk_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
All keys are prefixed with sk_ followed by a random alphanumeric string.

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Getting an API Key

  1. Sign in to your dashboard
  2. Navigate to API Keys
  3. Click Create API Key
  4. Give your key a descriptive name
  5. Copy the key immediately — it won’t be shown again
Treat your API key like a password. Do not expose it in client-side code, public repositories, or logs. If a key is compromised, revoke it immediately from your dashboard.

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Example Request

curl https://api.modelstack.cc/v1/chat/completions \
  -H "Authorization: Bearer [your_api_key]" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-4-5",
    "messages": [{"role": "user", "content": "Hello!"}]
  }'

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API Key Limits

The number of API keys you can create depends on your plan:
PlanMax API Keys
Starter5
Pro20
MaxUnlimited

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Security Best Practices

Store your API key in environment variables rather than hardcoding it:
export MODELSTACK_API_KEY="your_api_key"

import os
api_key = os.environ["MODELSTACK_API_KEY"]
Create distinct API keys for development, staging, and production. This lets you revoke a compromised key without affecting other environments.
Rotate your API keys regularly. Create a new key, update your applications, then revoke the old key.
Add .env files to .gitignore and use secret management tools for production deployments.

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Error Responses

If authentication fails, the API returns a 401 Unauthorized error: 
{
  "error": {
    "message": "Invalid API key provided",
    "type": "authentication_error",
    "code": 401
  }
}