Which messengers require a phone number or email?
A nine-service audit that separates the identifier used to create an account from the information a user can later hide from contacts.
SECURITY RESEARCH & OPEN DATA
Research that shows its work
Original City of Hats documentation audits with narrow questions, reproducible methods, first-party sources, visible uncertainty, and downloadable data.
Methods, sources, limitations, and corrections publishedDOCUMENTATION AUDIT · AUGUST 2026
Latest research
Research standards
Each report defines a testable question instead of hiding a broad product ranking behind a score.
Vendor documentation, technical papers, and official announcements are preferred over search snippets or summaries.
Regional differences, inaccessible evidence, and first-party City of Hats claims remain labeled in the result.
Machine-readable datasets include sources, notes, dates, and classification codes for independent review.
Independent review is still necessary
City of Hats funds and publishes this research. A transparent method makes claims easier to inspect; it does not turn our work into an independent security audit or neutral market ranking.
City of Hats funds and publishes this research. A transparent method makes claims easier to inspect; it does not turn our work into an independent security audit or neutral market ranking.