Phone line types explained: mobile, landline, and VoIP

A phone number tells you less than it seems to. Before you call or text a list of businesses, it helps to know which numbers are mobile, which are landlines, and which run over the internet. This article explains the three labels, where Prospect Locally gets them at no cost, why the difference matters, and when it is worth paying for a live lookup.

What the labels mean

• Mobile. The number belongs to a cellular line. It can receive text messages, and a call to it usually reaches a person who carries the phone. For a small business, a mobile number is often the owner’s own phone.
• Landline. The number belongs to a fixed line, such as a shop counter or an office desk. It can receive calls, but it generally cannot receive text messages.
• VoIP. The number runs over the internet through a provider of voice-over-IP service. It may ring a desk phone, an app, or a call-forwarding service, and whether it accepts text messages depends on the provider. Many small businesses use VoIP numbers because they cost less than a landline and can follow the owner anywhere.

A fourth label, toll-free, marks numbers such as the 800 range. A toll-free number usually reaches a main line or a call center rather than an individual.

Why the type matters

The label changes what you can do, and what the law lets you do. A text message to a landline fails, so a texting campaign that includes landlines wastes effort and skews your results. A call to a mobile number reaches a person away from the desk, which can help or hurt depending on the hour and the message. Rules on calls and texts also differ by line type in some countries, so a sender needs to know the type before choosing a channel. The sender stays responsible for following the rules where the recipient lives, including consent and do-not-call registries.

Where the free labels come from

For numbers in the United States and Canada, Prospect Locally reads North American number-block data. The numbering authorities for each country publish which carrier holds each block of a thousand numbers, and a lookup against that data gives the carrier and a type for the block. For numbers in other countries, the search uses the metadata in libphonenumber, an open-source library for parsing and classifying phone numbers.

These labels cost nothing per lookup, so every phone number in every search comes back labelled. They come with one limit. The data describes how a block of numbers was assigned, not what happened to a single number afterward. If a customer moved a number to another carrier, or a business ported a landline to an internet service, the block data may not know. Treat the free label as a good first filter.

International numbers keep their own format. The search never reformats a ten-digit number from outside the United States as if it were a US number.

What you see in the results

Each number appears with a type pill and a carrier. The results table shows mobile numbers in green, VoIP numbers in amber, and other types in blue. The With mobile quick filter keeps the businesses that have a mobile number, and a sort on the phone type column groups the types together. A business can have several numbers, so the Contact tab of its profile lists each one, with the Google profile number first.

When to verify a number

A live lookup asks a carrier database about one specific number right now. In Prospect Locally it is called Verify. It is available to accounts on a paid plan, and it costs 5 credits per number. Use it where a wrong label costs more than the credits, for example:

• before a text campaign to a short list of high-value leads,
• before you hand numbers to a caller who will work them for a day,
• or for a number whose free label looks doubtful, such as a VoIP number at a business you expected to use a landline.

To verify, tick the rows in the results table and press Verify numbers, or press Verify beside a number in the Contact tab of a business profile. A dialog appears before any charge. It states how many numbers it will look up, the cost in credits, and your balance afterward, and you confirm with Verify.

Three rules keep the cost predictable. A number you verified in the last 30 days is skipped and costs nothing. A lookup that fails because of a transport error, an unprocessable number, or an answer with no carrier data is refunded. And the verified type replaces the free label everywhere, in the table, the profile, the filters, and every CSV export, with a check mark on the pill and a “Verified on” date on the profile.

A sensible order of work

1. Run the search and read the free labels.
2. Filter to the businesses and number types your campaign can use.
3. Verify only the numbers that survive the filter and matter most.
4. Export the result, and contact each number through the channel its type supports.

You can run the same lookups from code through the API. The documentation describes the verify endpoint, and you can try a search from the home page to see the labels on real businesses.