Line Type Intelligence: Mobile vs. Landline vs. VoIP vs. Toll-Free
Updated July 26, 2026 · 5 min read
Line type is one of the most useful signals you can attach to a phone number. It tells you whether you can text it, whether it's likely a person or a business, and how much fraud risk it carries. Here's what each type means and how to act on it.
The four line types
Most numbers resolve to one of four categories, and each one changes how you should treat the number:
- Mobile — can receive SMS and calls; the default target for text campaigns and OTPs.
- Landline — voice only; texting it wastes spend and won't be delivered.
- VoIP — an internet-based line; usable but carries higher fraud risk and may not support SMS reliably.
- Toll-free — a business number; useful for support routing, not for outbound personal outreach.
Why line type changes your decisions
Routing is the first payoff: send SMS to mobile numbers and route landlines to a voice channel instead of burning texts that can't land. The second payoff is risk: VoIP weighs into a fraud score because it's the line type most associated with abuse.
Line type also affects cost. Texting landlines and unsupported VoIP lines is spend with no chance of delivery — filtering by line type removes that waste before it happens.
Line type and ported numbers
A number's line type isn't fixed forever. Numbers get ported between carriers, and the original allocation can be misleading — a number that started on one carrier may now live on another, or route through a VoIP gateway.
That's why resolving line type against current network data matters. Reading the original allocation can tell you the number is a landline when it's actually been ported to a mobile or VoIP carrier.
Key takeaways
- The four line types — mobile, landline, VoIP, toll-free — each imply a different action.
- Route SMS to mobile, send landlines to voice, and weigh VoIP into a risk score.
- Filtering by line type removes spend that could never be delivered.
- Resolve line type against current data, since porting can change it.
Key terms
Frequently asked
Can I send SMS to a VoIP number?+
Sometimes. Some VoIP providers support SMS and some don't, so delivery is less reliable than to a mobile number. Because VoIP also carries higher fraud risk, many teams treat VoIP as a signal to verify more carefully rather than a guaranteed SMS target.
Why does a number's line type sometimes look wrong?+
Usually because it was read from the number's original allocation rather than current network data. Numbers get ported between carriers, so resolving line type live is the only way to reflect where the number actually lives today.