Understanding the difference between mobile vs VoIP vs landline numbers is essential for any business that sends text messages, makes outbound calls, or verifies users by phone. Phone line type detection tells you whether a number can receive SMS, whether it belongs to a disposable VoIP service, or whether it is a fixed landline that will silently drop your message. Without this data, you waste budget on undeliverable messages and risk compliance violations.
The Three Main Line Types
When a user provides a phone number, it typically falls into one of three categories:
1. Mobile (Wireless)
- Assigned to a SIM card or eSIM
- Can receive SMS and voice calls
- Often used for personal or primary contact
- Supports two-factor authentication, marketing messages, etc.
2. VoIP (Voice over IP)
- Hosted by internet-based carriers (e.g. Google Voice, Skype, Twilio)
- May support SMS, but not always reliably
- Often used for business, call centers, or lead fraud
- Can be disposable or used to mask real identity
3. Landline
- Fixed location numbers (e.g. home phones, office lines)
- Cannot receive SMS
- Still common in enterprise, healthcare, or government settings
Why Line Type Matters
Trying to message or verify the wrong line type can result in:
- Failed SMS delivery — Landlines and many VoIP numbers don’t support texting
- Wasted spend — You still get charged for undelivered messages or failed call attempts
- Skewed analytics — Invalid delivery data can distort your campaign performance
- Compliance risks — Some regulations (like TCPA in the U.S.) prohibit auto-dialing to certain line types without consent
By identifying the line type in advance, you can tailor how (or whether) you reach out.
Real-World Scenarios
Marketing Campaigns
Sending promo texts? Make sure you’re targeting mobile numbers only. Texting a landline is a waste of budget and won’t deliver.
Two-Factor Authentication (2FA)
Only mobile numbers can reliably receive one-time codes via SMS. VoIP numbers can introduce delays or spoofing risks. Landlines won’t receive them at all.
Lead Scoring and Fraud Prevention
VoIP numbers can signal risky behavior (like mass form submissions or disposable signups). Flagging those helps your sales team focus on real leads.
Compliance Checks
In the U.S., you need express written consent to call or text certain numbers. Knowing the line type helps ensure you stay compliant with TCPA rules.
How to Identify Line Type Automatically
Many businesses attempt to guess line type using area codes or carrier names — but this is unreliable and often outdated.
CheckThatPhone uses real-time carrier data and direct network queries to return accurate phone line type detection for every U.S. and Canadian number, including:
- Line type (mobile, VoIP, landline)
- Carrier name and subtype
- Routing and portability info
- Deliverability indicators
See the API documentation for the full response format and integration examples. This helps you automate filtering, scoring, or routing logic inside your CRM or marketing automation tools.
Getting Started
Line type affects message delivery, user experience, compliance, and business outcomes. Organizations that distinguish between mobile, VoIP, and landline numbers make smarter decisions, reduce costs, and improve communication effectiveness. CheckThatPhone makes phone line type detection simple — read the documentation to integrate line type checks into your workflow, or explore pricing plans to start validating numbers at the scale you need.