How can I tell if a phone number is a mobile or a landline?

You have to look it up against current carrier data; the number itself does not tell you. Because of number portability, a number originally issued as a landline can now be a mobile on a different network, and the area code and exchange prefix only describe the original block allocation. A line type lookup consults current assignment and portability data and returns whether the number is mobile, landline, VOIP or invalid.

Can you text a landline number?

Not in any useful sense. A landline has no mechanism for receiving SMS, so the message fails. Some carriers convert a text sent to a landline into an automated voice call that reads the message aloud, which is an unusual experience and almost never what the sender intended. Because you are charged per send attempt, texting landlines costs money and delivers nothing, which is why filtering them out before a campaign matters.

Why does the area code not tell me where a number is or what type it is?

Number portability broke the link. Subscribers can keep their number when switching carriers and when moving, so a number with a New York area code may sit on a mobile handset in Denver. The NPA-NXX prefix describes which carrier originally received that block of numbers, not who serves the individual number today or what kind of service it is. Only a lookup against current data answers either question.

Can VOIP numbers receive text messages?

Sometimes, and it depends entirely on the provider. Some VOIP services support SMS fully, others support it partially, and others accept the message and discard it without notifying the sender. That inconsistency is why VOIP is reported as its own line type rather than being grouped with mobile. Whether you include VOIP numbers in an SMS campaign is a judgement call about your tolerance for silent failures.

Does knowing line type help with TCPA compliance?

It is a necessary input, though not sufficient on its own. The TCPA applies stricter consent requirements to autodialled contact with mobile numbers than to landlines, so a list that does not distinguish the two cannot be routed correctly. Line type tells you which rules apply to which rows; your consent records and suppression lists tell you whether you may contact that person at all. You need both, and neither substitutes for legal advice.

How often does the line type of a phone number actually change?

For any individual number, rarely. Across a list of thousands, continuously. People switch carriers, port numbers between mobile and VOIP services, disconnect lines, and receive numbers that were reassigned from a previous owner. None of that generates a notification to you. The practical consequence is that a validation result is a snapshot with a shelf life, and lists that are not revalidated drift steadily back toward their original condition.

Line type

The classification of a phone number as mobile, landline, VOIP, or invalid.

Upload a CSV and validate your phone list

No account required · Results in under 60 seconds

Line type is the classification of a phone number by the kind of service behind it: mobile, landline, VOIP, or invalid. It is the single most useful attribute you can attach to a contact record, because it determines both what you are permitted to send and what can physically arrive.

The reason line type has to be looked up rather than inferred is number portability. Since subscribers gained the right to keep their number when switching carriers, the digits themselves stopped carrying reliable information about the service behind them. A number originally issued as a landline in 2004 may today be a mobile on a different network, or a VOIP line issued by a software company. Only a lookup against current carrier data can tell you which.

What is line type?

✓Mobile — terminates on a cellular network and can receive SMS and MMS.
✓Landline — fixed location on the traditional network, and cannot receive SMS.
✓VOIP — routed over the internet; SMS support depends entirely on the provider.
✓Invalid — misformatted, unassigned, or never allocated, and fails permanently.

A mobile number terminates on a cellular network and reaches a handset. It can receive SMS and MMS, and it is the only category reliably reachable by text. For most outreach programmes, mobile is the segment that matters.

A landline terminates on the traditional circuit-switched telephone network at a fixed location. It cannot receive SMS. Some carriers convert a text sent to a landline into an automated voice call that reads the message aloud, which is an odd experience and rarely the intended one.

A VOIP number routes over the internet rather than a carrier's radio or copper infrastructure. Whether it can receive SMS depends entirely on the provider: some support messaging fully, others partially, and others discard it silently. VOIP numbers are also disproportionately represented in fraud and throwaway signups, because they are cheap and easy to obtain in bulk.

An invalid number fails basic checks. It may be misformatted, use an unassigned area code or exchange prefix, or simply never have been allocated. These are permanent failures and belong in a suppression list rather than a retry queue.

Some data sources report finer distinctions, such as separating fixed VOIP issued by a traditional carrier from non-fixed VOIP issued by an app. That distinction matters for fraud scoring, because non-fixed VOIP is the category most associated with disposable numbers.

It is worth noting what line type does not tell you. It does not indicate whether a number is currently in service, whether the person who gave it to you still holds it, or whether you have permission to contact them. Those are separate questions answered by validity checks and consent records.

How line type works

A line type lookup queries data reflecting current number assignments rather than the historical block allocation encoded in the prefix. That is what makes the answer trustworthy after a number has been ported.

The starting point is the numbering plan. Blocks of numbers are allocated to carriers in NPA-NXX ranges, and public tables map those ranges to the carrier they were originally assigned to. If portability did not exist, this would be sufficient.

Portability data is the correction layer. When a number moves between carriers, the routing information is updated centrally so calls and messages reach the right network. A lookup that consults this data returns the carrier serving the number today rather than the one that originally received the block.

For mobile numbers, a network query can go further and establish whether the number is currently active and reachable, by consulting the register a mobile network maintains of its subscribers. This distinguishes an assigned, switched-on number from one that has been disconnected.

The output is typically a line type classification, a carrier name, a country, and a validity flag. Richer lookups add the mobile country and network codes, VOIP provider identification where applicable, and portability status.

Accuracy varies by data source and by country. US and Canadian numbers are generally well covered because the numbering plan is shared and portability data is centralised. Coverage elsewhere depends on what each country's carriers publish.

Results also age. A lookup is a snapshot of the moment it ran, and numbers are ported, disconnected and reassigned continuously, which is why a file validated a year ago should not be treated as current.

Watch out

Area code tells you nothing reliable about line type or location. Portability means a number with a New York area code can sit on a mobile in Denver, and a prefix that was allocated to a landline carrier a decade ago may now serve a VOIP line.

Why line type matters for SMS and outreach teams

Line type decides whether a message can arrive at all. Every SMS sent to a landline fails, so a list with ten percent landlines carries a ten percent deliverability ceiling before content, registration or reputation enter the picture.

Because SMS is billed per send attempt rather than per delivery, those failures are paid for in full. The cost is not only the wasted fee: carriers score senders on delivery outcomes, so a steady stream of failures degrades delivery for the reachable portion of the same list.

✓Deliverability — every SMS to a landline fails, capping your rate before content or reputation apply.
✓Cost — billing is per send attempt, so unreachable numbers are paid for in full and return nothing.
✓Compliance — the TCPA applies stricter consent rules to mobiles than to landlines.
✓Channel choice — mobiles are reachable by text and call, landlines by call only.
✓Fraud signal — non-fixed VOIP correlates with disposable numbers at signup.

It is also a compliance input. The consent rules under the TCPA that attach to a mobile number are stricter than those for a landline, which means a list that does not distinguish the two cannot be routed correctly. A business is then either over-restricting its landline outreach or under-protecting its mobile outreach.

Channel selection depends on it directly. A mobile number is reachable by text and by call. A landline is call-only. Routing a landline into an SMS sequence produces nothing, while routing a mobile into a voice-only workflow misses the channel that would have had the better response.

VOIP identification carries its own signal. A signup using a non-fixed VOIP number is not automatically fraudulent, but the category correlates strongly with disposable and throwaway usage, which makes it a useful input to risk scoring during account creation.

Finally, line type improves the data you already hold. Appending it to a CRM export turns an undifferentiated list of digits into a segmented one, which is the prerequisite for measuring performance by segment rather than guessing at aggregate numbers.

Getting started with line type

Export the numbers you hold and normalise the formatting first. Inconsistent local formats are a common source of duplicate records, and converting to the international E.164 format resolves most of it before any lookup runs.

1
Normalise the formatting — Convert everything to E.164 so two spellings of the same number stop being treated as two contacts.
2
Append line type as new columns — Add line type, carrier and validity beside your existing data rather than replacing it, so nothing is lost.
3
Segment on the result — Mobiles to SMS, landlines to call workflows, invalid and disconnected to suppression, VOIP by your risk tolerance.
4
Store a validated-on timestamp — Knowing when a number was last checked is what tells you when the answer has aged.
5
Check at signup, not only in batch — Catching a non-fixed VOIP number during registration is more useful than finding it in a quarterly cleanup.

Revalidate before significant campaigns. Numbers move between carriers, get disconnected and get reassigned continuously, so the value of a validation pass decays from the moment it completes.

Key takeaways: line type

✓Line type classifies a number as mobile, landline, VOIP or invalid, and determines what can be sent to it.
✓Only mobile numbers reliably receive SMS; landlines cannot, and VOIP support depends entirely on the provider.
✓Number portability means line type cannot be inferred from the digits and must be looked up against current carrier data.
✓Because SMS is billed per attempt, landlines and dead numbers cost full price and return nothing.
✓The TCPA applies different consent rules to mobiles than to landlines, making line type a compliance input.
✓A lookup is a snapshot; numbers are ported, disconnected and reassigned continuously, so results age.

Frequently asked questions about line type

How can I tell if a phone number is a mobile or a landline?
Can you text a landline number?
Why does the area code not tell me where a number is or what type it is?
Can VOIP numbers receive text messages?
Does knowing line type help with TCPA compliance?
How often does the line type of a phone number actually change?

Number portability — The ability to keep a phone number when switching from one carrier to another.
Carrier lookup — Querying network data to find which carrier currently serves a phone number.
SMS deliverability — The proportion of sent SMS messages that are actually delivered to a recipient handset.
PSTN — The Public Switched Telephone Network — the traditional circuit-switched phone system.
HLR lookup — A query against a mobile network Home Location Register to check whether a number is active and reachable.

Check your list before your next send

Upload a CSV and PhoneCheckr flags every mobile, landline, VOIP, and invalid number so you only pay to reach contacts who can actually receive your message.

Validate your phone list

Back to the full glossary