Guides

Everything you need to know about phone number verification — from basic format validation to real-time network queries, OTP security, fraud prevention, and choosing the right API.

1
Overview & Phone Number States
The three states every phone number occupies: Valid, Active, and Online.
 2
E.164 Format & Input Validation
International format standard and why regex fails for phone validation.
 3
API Validation & Line Type Intelligence
Tier 1 validation APIs, the NANP anomaly, and SMS routing optimization.
 4
HLR Lookups & Network Validation
How SS7 queries verify if numbers are active, ported, or roaming.
 5
OTP Verification & Security Threats
OTP mechanics, SIM swapping, SS7 attacks, and API bypass vulnerabilities.
 6
Fraud Prevention & Caller Identity
VoIP detection, IRSF prevention, CNAM, and Branded Calling technology.
 7
API Comparison & Implementation
Compare Veriphone, Twilio, Vonage, and Numverify. Waterfall architecture.