How many accounts can I register my YubiKey with?

 Note: 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.

YubiKey 5 Series firmware 5.7+

• FIDO2 - the YubiKey 5 can hold up to 100 discoverable credentials (AKA hardware-bound passkeys) in its FIDO2 application.
  
  
• FIDO U2F - similar to Yubico OTP, the FIDO U2F application can be registered with an unlimited number of services.
  
  
• PIV - the YubiKey 5's PIV (smart card) application has 4 usable slots per the PIV specification, each serving a specific purpose (authentication, digital signature, key management, and card authentication - click here for further information). In a Microsoft Windows environment and used in conjunction with the YubiKey Smart Card Minidriver, the number of usable certificates expands to approximately 12 (dependent upon many factors including algorithm used as well as various Certification Authority settings).
• OATH-TOTP - the YubiKey 5's OATH application can hold up to 64 OATH-TOTP credentials (AKA authenticator codes).
• 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.
  
  • The OTP application comes with:
    • Yubico OTP
    • Challenge-Response
    • Static Password
    • OATH-HOTP
• OpenPGP - the YubiKey 5's OpenPGP application can hold up to 3 subkeys (signature, encryption, authentication) linked to a single OpenPGP identity.

YubiKeys 5 Series with firmware 5.0-5.6

• FIDO2 - the YubiKey 5 can hold up to 25 discoverable credentials (AKA hardware-bound passkeys) in its FIDO2 application.
  
  
• FIDO U2F - similar to Yubico OTP, the FIDO U2F application can be registered with an unlimited number of services.
  
  
• PIV - the YubiKey 5's PIV (smart card) application has 4 usable slots per the PIV specification, each serving a specific purpose (authentication, digital signature, key management, and card authentication - click here for further information). In a Microsoft Windows environment and used in conjunction with the YubiKey Smart Card Minidriver, the number of usable certificates expands to approximately 12 (dependent upon many factors including algorithm used as well as various Certification Authority settings).
• OATH-TOTP - the YubiKey 5's OATH application can hold up to 32 OATH-TOTP credentials (AKA authenticator codes).
• OTP - this application can hold two credentials, can be registered with an unlimited number of services.
  
  • The OTP application comes with:
    • Yubico OTP
    • Challenge-Response
    • Static Password
    • OATH-HOTP
• OpenPGP - the YubiKey 5's OpenPGP application can hold up to 3 subkeys (signature, encryption, authentication) linked to a single OpenPGP identity.

I would like to know the account limits for a different YubiKey that's not listed here

For other YubiKeys/Security Keys, please see the device page for the specific model of key in our Knowledge Base - Device Specifications section.

Get in contact with our Support team

Feel free to open a support ticket here, our support team is happy help!