While tools such as https://www.whatsmydns.net/ can be great for spot-checking your DNS geolocation accuracy, you may still encounter results that do not route as expected. Generally, this occurs when the website's test endpoint is using a resolver that is located in a different region than the test endpoint. In this case, the geolocation filters route the request based on the location of the resolver that queried the authoritative nameservers. The exception to resolver-based geolocation is when EDNS client subnet (ECS) resolution is enabled and supported by the resolver. This enables more accurate resolution based on the location of the requester but results in additional queries. Refer to About the EDNS Client Subnet (ECS) DNS extension for details.
