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Every request to the LeadX API must include your API key in the header. Without it, your requests will be rejected with a 401 Unauthorized error. 
X-API-KEY: YOUR_API_KEY
Keep your key private; treat it like a password. Add the API key as a header with X-API-Key.
Terminal
curl -X POST "https://api.leadx.com/v1/companies" \
  -H "X-API-KEY: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"url": "company.com"}'
You can also use your API key along with the interactive tool in the Endpoints section of this documentation to:
  • Run API calls directly from your browser
  • Experiment with different endpoints and parameters
  • View live JSON responses
This makes it easy to test the API before adding it into your codebase.
Last modified on March 23, 2026