How many accounts can I register my YubiKey with?

If you are experiencing the error No Space Available in Yubico Authenticator, then you may have reached the account limit of your YubiKey for TOTP. YubiKeys from the 5 Series support 6 different protocols for two-factor authentication, each with its own limit on the number of accounts it can be associated with. Which protocol will be used with a given account varies from service to service (website, app, etc.).


You can find setup instructions, as well as which protocol(s) a particular service uses on that service's entry in the Works With YubiKey Catalog, (eg. Google Accounts). The limits for each protocol are summarized below.


  • OTP - this application can hold two credentials. However, Yubico OTP, one of the most popular kinds of credentials to put in this app, can be registered with an unlimited number of services.
  • FIDO U2F - similar to Yubico OTP, the U2F application can be registered with an unlimited number of services.
  • FIDO2 - the YubiKey 5 can hold up to 25 discoverable credentials (AKA hardware-bound passkeys) in its FIDO2 application.
  • OATH (Yubico Authenticator) - the YubiKey 5's OATH application can hold up to 32 OATH-TOTP credentials (AKA authenticator app codes).
  • *PIV - the YubiKey 5's PIV (smart card) application has 24 slots, each of which can hold one certificate and its corresponding private key (click here for further information).
  • *OpenPGP - the YubiKey 5's OpenPGP application can hold up to three OpenPGP private keys, one for encryption, one for signing, and one for authentication.

*OpenPGP and PIV are less-commonly used than OTP, U2F, FIDO2, and OATH


For other YubiKeys/Security Keys, please see the device page for the specific model of key in our KB's Devices section.


To get in touch with our support team, open a support ticket here.