authenticatorData Parser
Walk WebAuthn authenticatorData (§6.1). Splits rpIdHash | flags | signCount | AAGUID | credentialId | credentialPublicKey | extensions, and surfaces the BE / BS passkey state flags.
Input
Decoded
Paste authenticatorData.
All decoding runs locally.
About authenticatorData
authenticatorData is a binary structure produced by the authenticator. It carries the RP ID digest (anti-phishing anchor), a flags byte (UP, UV, BE, BS, AT, ED), a 32-bit signature counter, and on registration the attestedCredentialData. The BE/BS flags are the load-bearing fields for distinguishing device-bound credentials from syncable passkeys.
Spec
WebAuthn Level 2 §6.1.