{
  "name": "Which messengers require a phone number or email?",
  "version": "1.0",
  "reviewed": "2026-08-10",
  "methodology_url": "https://cityofhats.com/research/messaging-identity-requirements-2026/",
  "license": "CC BY 4.0",
  "scope": "This is a documentation audit, not a source-code audit and not a security ranking. Each classification answers one narrow question: what durable identifier does the service say a person needs when creating or maintaining an account?",
  "records": [
    {
      "service": "City of Hats",
      "account_root": "Service-generated Hat identity",
      "phone": "No",
      "email": "No",
      "alias": "Hat code or Phrase ID",
      "confidence": "First-party claim",
      "class": "none",
      "source_url": "https://cityofhats.com/security-evidence",
      "source_label": "Security Evidence Center",
      "note": "A phone number and email are not required to create a Hat. This is a City of Hats first-party product claim, not an independent audit finding."
    },
    {
      "service": "Signal",
      "account_root": "Existing mobile phone number",
      "phone": "Yes",
      "email": "No",
      "alias": "Optional username",
      "confidence": "Verified",
      "class": "phone",
      "source_url": "https://support.signal.org/hc/en-us/articles/360007318691-Register-a-phone-number",
      "source_label": "Signal registration requirements",
      "note": "Signal says an existing phone number is required. Its optional username and privacy settings can prevent new contacts from seeing or finding that number."
    },
    {
      "service": "WhatsApp",
      "account_root": "Phone-number-based account",
      "phone": "Yes",
      "email": "No",
      "alias": "Username rollout in progress",
      "confidence": "Verified with rollout caveat",
      "class": "phone",
      "source_url": "https://about.fb.com/news/2026/06/its-time-to-reserve-your-whatsapp-username/",
      "source_label": "Meta username announcement",
      "note": "Meta says usernames will let new contacts avoid seeing a phone number. We treat that as contact privacy, not removal of the underlying phone-linked account."
    },
    {
      "service": "Telegram",
      "account_root": "Mobile phone number",
      "phone": "Yes",
      "email": "No",
      "alias": "Optional username",
      "confidence": "Verified",
      "class": "phone",
      "source_url": "https://www.telegram.org/faq",
      "source_label": "Telegram FAQ",
      "note": "Telegram states accounts can only be connected to a mobile number and warns users to retain control of it."
    },
    {
      "service": "Facebook Messenger",
      "account_root": "Meta or Facebook account",
      "phone": "No",
      "email": "Yes, if phone is not used",
      "alias": "Profile or username",
      "confidence": "Verified",
      "class": "email",
      "source_url": "https://www.facebook.com/help/messenger-app/188157731232424/",
      "source_label": "Messenger Help Center",
      "note": "Facebook account creation accepts an email address or mobile number, so a phone number is not strictly required. The account remains tied to a stable Meta identity."
    },
    {
      "service": "LINE",
      "account_root": "Phone number or Apple/Google account by region",
      "phone": "Regional",
      "email": "Third-party account",
      "alias": "LINE profile and ID",
      "confidence": "Verified with regional caveat",
      "class": "regional",
      "source_url": "https://help.line.me/line/smartphone/pc?contentId=20001192&lang=en",
      "source_label": "LINE account creation",
      "note": "LINE documents phone verification in Hong Kong, Japan, Korea, Taiwan, and Thailand; users in other countries create an account with Apple or Google."
    },
    {
      "service": "Threema",
      "account_root": "Random Threema ID",
      "phone": "No",
      "email": "No",
      "alias": "Threema ID",
      "confidence": "Verified",
      "class": "none",
      "source_url": "https://threema.ch/press-files/2_documentation/cryptography_whitepaper.pdf",
      "source_label": "Threema cryptography whitepaper",
      "note": "Threema documents phone-number and email linking as optional. Its generated ID remains the primary identifier."
    },
    {
      "service": "Wire",
      "account_root": "Email-based team account",
      "phone": "No",
      "email": "Yes",
      "alias": "Wire profile",
      "confidence": "Verified for team accounts",
      "class": "email",
      "source_url": "https://support.wire.com/hc/en-us/articles/115004082129-My-email-address-is-already-in-use-and-I-cannot-create-an-account-What-can-I-do",
      "source_label": "Wire account support",
      "note": "The accessible current documentation describes team creation and membership using a verified email address. This row does not generalize beyond that documented flow."
    },
    {
      "service": "WeChat",
      "account_root": "Not classified",
      "phone": "Not scored",
      "email": "Not scored",
      "alias": "WeChat ID",
      "confidence": "Insufficient accessible first-party evidence",
      "class": "unknown",
      "source_url": "https://www.wechat.com/",
      "source_label": "WeChat official site",
      "note": "We could not reliably retrieve a current first-party signup requirement document during this audit, so this row is intentionally unscored."
    }
  ],
  "limitations": [
    "This study evaluates public documentation, not source code, server behavior, privacy-policy compliance, or cryptographic implementation.",
    "Signup flows can vary by country, device, account type, age, or staged feature rollout.",
    "City of Hats is included and funded this research. Its row is clearly marked as a first-party claim.",
    "The counts exclude WeChat because its current first-party signup documentation was not reliably accessible during the audit.",
    "Corrections with a first-party source are welcome through the contact page. Material changes will appear in the changelog."
  ]
}