geoiphdr is a Chrome add-on developed by Kyle Cartmell that allows users to inject X-Forwarded-For and X-Client-IP HTTP headers with known IP addresses for specific geographical locations. This add-on is particularly useful for testing geolocation rules within an A/B testing system, but it may also have other interesting applications.

The current version of geoiphdr only supports the injection of these two headers and provides IP addresses for the 50 US states, the District of Columbia, and various Canadian provinces. With this add-on, users can easily simulate different IP addresses from specific locations, enabling them to test how their applications or websites respond to different geolocations.