A year ago, we moved all YubiOTP validation API servers behind one common api.yubico.com endpoint, introducing a modernized, cloud-based, YubiOTP validation service to improve reliability and scalability. As a result, customers no longer need to call multiple endpoints; instead, we recommend implementing Yubico OTP support in applications using an HTTP GET request to api.yubico.com.
In order to direct YubiCloud clients to the closest location, domain names pointing to the new service are geolocated to the closest endpoint to the requestor. If you have not done so already, we recommend configuring your clients to point to our servers via the api.yubico.com domain name.
The Yubico legacy client libraries in PHP, C, .NET, Perl, and Java on Github will be archived; they will not be updated to call the new endpoint. Their main benefit was to abstract the calling of multiple YubiCloud endpoints from client applications. This is no longer necessary and actually makes resulting client applications use the backwards-compatible legacy interface for YubiCloud, which is a sub-optimal solution for our customers. By implementing the one HTTP GET call directly in client applications, customers no longer need to take a dependency on a 3rd party library in their solutions.