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API Keys

Transmit uses API keys to authenticate requests. You can create and manage your API keys in the Dashboard.
Your API keys carry many privileges, so be sure to keep them secure! Do not share your secret API keys in publicly accessible areas such as GitHub, client-side code, and so on.

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Authentication Methods

Pass your API key in the Authorization header with the Bearer scheme: 
curl https://api.transmit.dev/v1/emails \
  -H "Authorization: Bearer tx_your_api_key_here"

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Using SDKs

Our SDKs automatically handle authentication. Just provide your API key when initializing the client: 
import { TransmitClient } from '@transmit.dev/sdk';

const client = new TransmitClient({
  apiKey: process.env.TRANSMIT_API_KEY
});

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API Key Types

Transmit supports different types of API keys:
Use live keys in production. They start with tx_live_.
  • Can send real emails
  • Charges your account
  • Full access to production data
Use test keys in development. They start with tx_test_.
  • Simulates sending without actual delivery
  • No charges
  • Separate test data environment

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Best Practices

Use Environment Variables

Store API keys in environment variables, never in your code
# .env
TRANSMIT_API_KEY=tx_your_api_key_here

Rotate Keys Regularly

Generate new keys periodically and revoke old ones

Use Different Keys per Environment

Separate keys for development, staging, and production

Monitor API Key Usage

Check the dashboard for unusual activity on your keys

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Testing Authentication

Test that your API key is working correctly: 
curl https://api.transmit.dev/v1/emails \
  -H "Authorization: Bearer tx_your_api_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "hello@yourdomain.com",
    "to": "test@example.com",
    "subject": "Test",
    "html": "<p>Testing authentication</p>"
  }'
If authentication succeeds, you’ll receive a 200 OK response with the email ID.

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Error Responses

Status CodeErrorDescription
401unauthorizedMissing or invalid API key
403forbiddenAPI key doesn’t have required permissions
429rate_limit_exceededToo many requests
Example error response: 
{
  "error": {
    "code": "unauthorized",
    "message": "Invalid API key provided"
  }
}

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Rate Limits

API rate limits vary by plan:
  • Free: 100 requests/hour
  • Starter: 1,000 requests/hour
  • Pro: 10,000 requests/hour
  • Enterprise: Custom limits
Rate limits are per API key. Contact support if you need higher limits.
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