If your business sends SMS, places calls, or verifies phone numbers, knowing what kind of number you’re contacting is critical. Mobile, VoIP, and landline numbers behave differently — and not all of them will support your communication goals.
In this article, we’ll break down the key differences between line types, why they matter for delivery, cost, and compliance, and how to identify them in real time.
📞 What Are the 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 & 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, up-to-date information for every U.S. and Canadian number, including:
- Line type (mobile, VoIP, landline)
- Carrier name and subtype
- Routing and portability info
- Deliverability indicators
This helps you automate filtering, scoring, or routing logic inside your CRM or marketing automation tools.
✅ Summary
Line type is more than a technical detail — it directly affects message delivery, user experience, compliance, and your bottom line. Businesses that understand the difference between mobile, VoIP, and landline numbers can make smarter decisions, save money, and improve communication outcomes.
If you’re ready to filter by line type with confidence, try CheckThatPhone’s real-time phone intelligence API today.
👉 Start your free trial and identify the right numbers before you hit send.