Developers
How to check if a phone number is on WhatsApp with an API
How a WhatsApp registration check works, what registered, not registered and unknown mean, and how to call it responsibly from cURL, Node and Python.
8 min read
Articles tagged “WhatsApp”
4 articles.
Guides
Messaging-app registration checks: a guide for every app
What a registration check tells you for WhatsApp, Telegram, Viber, Signal, iMessage, RCS, LINE, Zalo and more: modes, unknowns, billing and consent.
8 min read
Guides
WhatsApp Business account check: what the business flag tells you (and what it doesn't)
What the WhatsApp Business flag means, how it differs from a personal account, its limits, and how B2B and support teams can use it responsibly.
7 min read
Deliverability
WhatsApp OTP vs SMS OTP: cost per verified user, with a calculator
WhatsApp authentication rates vs SMS prices by country, the October 2026 changes, and a calculator for cost per verified user including SMS fallback.
7 min read
