Apple has informed developers that the legacy TestFlightApp.com beta testing service will shut down on February 26:

The services offered at TestFlightApp.com will no longer be available after February 26, 2015. To prepare for the TestFlightapp.com closure, developers and team leaders are recommended to transfer their testers to the all-new TestFlight Beta Testing in iTunes Connect.

The legacy TestFlight website has continued working in spite of Apple’s acquisition of TestFlight last year and subsequent integration in iTunes Connect. Apple is providing developers with instructions to migrate existing testers to the new TestFlight service, with more details available here.

As I wrote last week, the new TestFlight is not perfect, but its native presence on iOS 8 offers a superior solution for testers and developers thanks to the reliance on Apple IDs. Notably, the legacy TestFlight website allowed developers to release betas for devices running older versions of iOS, whereas the new TestFlight is only available for iOS 8.