During the last few years, the FIDO Alliance and the W3C have been working on a new standard calledWebAuthn that aims to substitute the obsolete password as an authentication method by using physical security keys instead. Due to its recent design, the standard is still changing and so are the needs for protocol testing. This research has driven the development of a web application that supports the standard and gives extensive information to the user. This tool can be used by WebAuthn developers and researchers, helping them to debug concrete use cases with no need for an ad hoc implementation.