Hey @Browse1236
you did not mention which Nitrokey you use, thus I am assuming Nitrokey 3, but the information should widely be the same for Nitrokey FIDO2 devices. I’ll be making this short (and trivialized), please check the linked article at the end for more details.
Generally there are 2 ways to store credentials on (NK3s) FIDO2 devices:
- U2F
- FIDO2 / Resident Keys / “Discoverable Credential”
Most services use 1), these cannot be listed and basically there are unlimited of these to be kept on the Nitrokey 3 as the credentials are “derived” from a unique “secret” (Attention: simplified, but roughly that’s it)
For the Resident Keys 2) this looks different, you can e.g., list them (e.g., through: chrome://settings/securityKeys ) Sign-in data and there is an upper limit how many of these can be stored (currently 20) …
You can try out both methods using webauthn.io by opening “advanced settings” and switching of the respective drop-downs to “discouraged” (for discoverable credentials).
So generally I would highly recommend to have at least 2 devices registered with any service, usually you will never hit a limit doing so.
I would also recommend to read FIDO2, WebAuthn, Passkeys in 2022 and 2023 | Nitrokey - it comes with some more background information.
best