Signal Number Validation & Identity Lookup — Try the interactive demo

The lightest, fastest call: returns only whether a phone number is a registered Signal account, without fetching identity metadata. Ideal for real-time form validation, sign-up gating, and high-volume list screening. Pass the full international number (digits, optional leading +); the API normalizes to digits only. registered is three-state: true = registered, false = not registered, null = undetermined (transient — see message, e.g. timeout).

Full lookup for a single number: registration status plus the public identity of the account when registered — ACI (Account Identifier UUID), PNI (Phone Number Identifier, usually PNI:<uuid>), optional plaintext profile metadata (identityKey, unrestrictedUnidentifiedAccess, capabilities, badges), a machine status (found / not_found / timeout / ...), a human-readable message, and durationMs. fieldsEncrypted=true for strangers indicates that display name / about / avatar are withheld by Signal's end-to-end profile encryption (not a tool limitation). Use this when you need identity enrichment, not just a yes/no.

Fetch unversioned public profile metadata for a known ACI (UUID). Returns plaintext fields only: identityKey, unidentifiedAccess, unrestrictedUnidentifiedAccess, capabilities, badges, and uuid (same as ACI). Name / about / avatar are never present on this path for non-contacts. Obtain the ACI first via the user-info endpoint.