Callook: USA Amateur Radio Callsign Lookup

Callook provides a USA amateur radio callsign lookup service with data current as of March 25, 2026. The platform allows users to search for valid callsigns and retrieve detailed information, including geographic coordinates sourced from the Bing Maps API. A mathematically calculated grid square is derived from these coordinates, though accuracy is not guaranteed due to reliance on external services. The service supports multiple access methods, including a browser search plugin, direct API access with a reference, and plain text output for integration into other applications or scripts.

This tool facilitates rapid identification of US amateur radio operators, offering an alternative to other callbook services. Its API access enables developers to integrate callsign lookup functionality into custom applications, streamlining data retrieval for logging software or contest management. The direct presentation of FCC data, combined with grid square calculation, assists DXers and contesters in verifying contact information and location details during on-air operations.