| appid | This authentication extension allows WebAuthn Relying Parties that have previously registered a credential using the legacy FIDO JavaScript APIs to request an assertion. | [Web Authentication] Section §10.1, FIDO AppID Extension (appid) | [W3C_Web_Authentication_Working_Group] | |
| txAuthSimple | This registration extension and authentication extension allows for a simple form of transaction authorization. A WebAuthn Relying Party can specify a prompt string, intended for display on a trusted device on the authenticator | [Web Authentication] Section §10.2, Simple Transaction Authorization Extension (txAuthSimple) | [W3C_Web_Authentication_Working_Group] | |
| txAuthGeneric | This registration extension and authentication extension allows images to be used as transaction authorization prompts as well. This allows authenticators without a font rendering engine to be used and also supports a richer visual appearance than accomplished with the webauthn.txauth.simple extension. | [Web Authentication] Section §10.3, Generic Transaction Authorization Extension (txAuthGeneric) | [W3C_Web_Authentication_Working_Group] | |
| authnSel | This registration extension allows a WebAuthn Relying Party to guide the selection of the authenticator that will be leveraged when creating the credential. It is intended primarily for WebAuthn Relying Parties that wish to tightly control the experience around credential creation. | [Web Authentication] Section §10.4, Authenticator Selection Extension (authnSel) | [W3C_Web_Authentication_Working_Group] | |
| exts | This registration extension enables the WebAuthn Relying Party to determine which extensions the authenticator supports. The extension data is a list (CBOR array) of extension identifiers encoded as UTF-8 Strings. This extension is added automatically by the authenticator. This extension can be added to attestation statements. | [Web Authentication] Section §10.5, Supported Extensions Extension (exts) | [W3C_Web_Authentication_Working_Group] | |
| uvi | This registration extension and authentication extension enables use of a user verification index. The user verification index is a value uniquely identifying a user verification data record. The UVI data can be used by servers to understand whether an authentication was authorized by the exact same biometric data as the initial key generation. This allows the detection and prevention of "friendly fraud". | [Web Authentication] Section §10.6, User Verification Index Extension (uvi) | [W3C_Web_Authentication_Working_Group] | |
| loc | The location registration extension and authentication extension provides the client device's current location to the WebAuthn Relying Party, if supported by the client platform and subject to user consent. | [Web Authentication] Section §10.7, Location Extension (loc) | [W3C_Web_Authentication_Working_Group] | |
| uvm | This registration extension and authentication extension enables use of a user verification method. The user verification method extension returns to the WebAuthn Relying Party which user verification methods (factors) were used for the WebAuthn operation. | [Web Authentication] Section §10.3, User Verification Method Extension (uvm) | [W3C_Web_Authentication_Working_Group] | |
| credProtect | This registration extension allows relying parties to specify a credential protection policy when creating a credential. Additionally, authenticators may choose to establish a default credential protection policy greater than userVerificationOptional (the lowest level) and unilaterally enforce such policy. | [Client to Authenticator Protocol (CTAP)] Section §12.1 Credential Protection (credProtect) | [W3C_Web_Authentication_Working_Group] | |
| credBlob | This registration extension and authentication extension enables RPs to provide a small amount of extra credential configuration information (the credBlob value) to the authenticator when a credential is made. | [Client to Authenticator Protocol (CTAP)] Section §12.2 Credential Blob (credBlob) | [W3C_Web_Authentication_Working_Group] | |
| largeBlobKey | This client platform-only extension provides for storage and retrieval of a per-credential key that is used by the client platform when writing and reading elements in the large-blob array. | [Client to Authenticator Protocol (CTAP)] Section §12.3 Large Blob Key (largeBlobKey) | [W3C_Web_Authentication_Working_Group] | |
| minPinLength | This registration extension returns the current minimum PIN length value to the Relying Party. | [Client to Authenticator Protocol (CTAP)] Section §12.4 Minimum PIN Length Extension (minPinLength) | [W3C_Web_Authentication_Working_Group] | |
| hmac-secret | This registration extension and authentication extension enables the platform to retrieve a symmetric secret scoped to the credential from the authenticator. | [Client to Authenticator Protocol (CTAP)] Section §12.5 HMAC Secret Extension (hmac-secret) | [W3C_Web_Authentication_Working_Group] | |
| appidExclude | This registration extension allows WebAuthn Relying Parties to exclude authenticators that contain specified credentials that were created with the legacy FIDO U2F JavaScript API [FIDOU2FJavaScriptAPI]. | [Web Authentication] Section §10.2, FIDO AppID Exclusion Extension (appidExclude) | [W3C_Web_Authentication_Working_Group] | |
| credProps | This client registration extension enables reporting of a newly-created credential's properties, as determined by the client, to the calling WebAuthn Relying Party's web application. | [Web Authentication] Section §10.4, Credential Properties Extension (credProps) | [W3C_Web_Authentication_Working_Group] | |
| largeBlob | This client registration extension and authentication extension allows a Relying Party to store opaque data associated with a credential. | [Web Authentication] Section §10.5, Large blob storage extension (largeBlob) | [W3C_Web_Authentication_Working_Group] | |
| payment | This extension supports the following functionality defined by the Secure Payment Confirmation API: (1) it allows credential creation in a cross-origin iframe (2) it allows a party other than the Relying Party to use the credential to perform an authentication ceremony on behalf of the Relying Party, and (3) it allows the browser to identify and cache Secure Payment Confirmation credentials. For discussion of important ways in which SPC differs from Web Authentication, see in particular [Secure Payment Confirmation §10 Security Considerations] and [Secure Payment Confirmation §11 Privacy Considerations]. | [Secure Payment Confirmation] Section §5, WebAuthn Extension - "payment" | [W3C_Web_Payments_Working_Group] | |
