What is a VoIP number?
A VoIP number routes calls over the internet instead of the mobile or fixed network — Google Voice, Skype numbers, cloud PBX lines. Cheap and flexible, and a key line-type signal in fraud scoring.
Definition
A VoIP (Voice over IP) number is a phone number whose traffic is carried over the internet rather than the circuit-switched mobile or fixed network. Consumer examples are Google Voice and Skype numbers; business examples are the DID ranges behind cloud PBXes and contact-centre platforms. To callers a VoIP number is indistinguishable from any other — it has a normal E.164 form and often a local city prefix — but in numbering databases it belongs to ranges allocated to VoIP carriers, which is how line-type lookups classify it.
VoIP numbers overlap heavily with virtual numbers — most virtual numbers are technically VoIP — but the term emphasises the transport. Operationally, SMS delivery to VoIP ranges is patchy (many VoIP carriers have limited or no SMS interconnect), latency and caller-ID behaviour differ, and in risk terms VoIP ranges see disproportionate use in fake registrations because acquiring them requires no identity and no SIM. Line-type classification — mobile vs fixed vs VoIP — is therefore a standard first-pass filter in verification and antifraud pipelines.
Why it matters
Treating all numbers alike means sending OTPs into VoIP ranges where they may never deliver, and trusting verifications from numbers that cost the attacker nothing. Line-type awareness fixes both — route real mobiles normally, challenge or block VoIP where your risk model says so.
See it in action
Classify line type with phone rating →