Carrier and line type lookup, explained

A carrier and line type lookup tells you two things about a phone number: what kind of line it is (mobile, landline, VoIP, toll-free and so on) and which network serves it today. The important word is today. A number's prefix only shows the network its range was originally allocated to. After porting, the current network can be different, and so can the line type. This guide explains where that data comes from, how to read each field, and how MobileValidate's carrier lookups answer.

#What is carrier and line type data?

It is descriptive data about a number, not about a person or a handset. Two fields do most of the work:

• Line type says what kind of service the number belongs to. It decides whether an SMS can arrive, what a call costs and which rules apply. The line type glossary entry lists every value.
• Carrier names the network that serves the number. It decides how messages are routed and priced, and it's a useful signal for fraud and data quality.

Neither field tells you whether the phone is switched on, who owns the number or whether it has been reassigned to a new subscriber. Those are different questions with different checks, as our guide on how to check if a number is active explains.

#Where does carrier and line type information come from?

From three kinds of source, each with a different view of the number.

Numbering plans. The international structure of phone numbers is defined in ITU-T Recommendation E.164, currently in its February 2026 edition (ITU, 2026). Within that structure, each country's regulator allocates blocks of numbers to operators and designates which ranges are mobile, geographic, toll-free, premium rate and so on. Offline libraries such as libphonenumber encode this: its getNumberType distinguishes fixed-line, mobile, toll-free, premium rate, shared cost, VoIP, personal numbers, UAN, pager and voicemail "whenever feasible". That's the range, not today's service.

Network identifiers. Mobile networks are identified by a mobile country code and a mobile network code under ITU-T E.212 (ITU, 2024). Together they form the MCC-MNC, which pins down a specific network rather than a brand name.

Porting records. In countries with number portability, operators keep track of numbers that moved to another network, so calls and messages can still be routed. Those records are what turn "allocated to network A" into "served by network B today".

A carrier lookup combines these views. The result is only as good as the underlying data for that country, which is why coverage varies and why a lookup should say "no data" rather than fall back to a guess based on the prefix.

#What is the difference between the allocated carrier and the current one?

The allocated carrier is the network a number's range was originally given to. The current carrier is the one serving the number now. Before portability they were the same. Today they often aren't.

In the US, the FCC's deadline for wireless local number portability was 24 November 2003. The FCC describes wireless LNP as a consumer's ability to change service providers within the same local area and keep the same number, and notes that it also allows moving a number from a wireline phone to a wireless phone in some cases (FCC). So a US number's area code and exchange tell you where it was first assigned, not which carrier or even which kind of line it is on now.

That has two practical effects:

• Carrier can change without any change to the digits. Routing and pricing by prefix then go wrong.
• Line type can change too, for example from landline to mobile, or from mobile to a VoIP service.

Our post on why carrier lookups can be wrong after porting covers porting mechanics and failure modes in depth.

#What does each line type mean for your decision?

The value matters less than what you do with it. A practical reading:

VoIP deserves a note. It is a legitimate service used by many real people, and NIST's current authentication guidance removed its earlier prohibition on VoIP numbers for out-of-band authentication (NIST, 2025). Our VoIP detection guide explains how to use it proportionately.

#How does the MobileValidate carrier lookup respond?

The carrier lookup (network.carrier, alias carrier) works for numbers in every country, in real time and in bulk jobs. It is labelled beta because coverage varies by country. It returns data in attributes:

An answer is conclusive only when carrier is present. Attributes we don't hold are left out rather than guessed. Here is a real test-mode request with four numbers:

curl https://api.mobilevalidate.com/v1/lookup \
  -H "Authorization: Bearer $MOBILEVALIDATE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"numbers": ["+447700900001", "+447700900002", "+447700900003", "+14155552671"],
       "checks": ["carrier"], "wait": 5}'

The four network.carrier results, trimmed:

{"status": "completed", "registered": true, "attributes": {"line_type": "mobile", "carrier": "Test Carrier", "country": "GB"}, "billed": false, "reason": null}
{"status": "unknown",   "registered": null, "attributes": null, "billed": false, "reason": "NO_DATA"}
{"status": "unknown",   "registered": null, "attributes": null, "billed": false, "reason": "UPSTREAM_TIMEOUT"}
{"status": "completed", "registered": true, "attributes": {"line_type": "mobile", "carrier": "Test Carrier", "country": "US"}, "billed": false, "reason": null}

Three things to notice. A conclusive data answer has registered: true, which here means "data found", not "registered on an app". A number we hold nothing for comes back unknown with reason: "NO_DATA", and a slow source gives UPSTREAM_TIMEOUT. You're not charged for inconclusive results (unknown, unsupported country, timeout, invalid, duplicate). Test data never includes a port, so original_carrier doesn't appear here. In live answers it appears when the number has moved.

#How should you read carrier names?

As labels, not as keys. Carrier names come with some traps:

• Virtual operators. Many retail brands run on another company's network. The lookup can return the network operator's name, which differs from the brand on the customer's bill.
• Mergers and rebrands. Operator names change over time. Two spellings can refer to the same network.
• Resellers of VoIP numbers. The name may be a wholesale provider rather than the app the person uses.

So avoid hard-coding exact string matches in routing or fraud rules. Group names into your own normalized list, review unknown names regularly, and rely on line_type for decisions about what kind of line it is. The HLR lookup, coming soon, will add the current network's mcc_mnc, which is a stable code rather than a name.

#When should you use the US/CA premium lookup?

When most of your numbers are in the United States or Canada and you work with lists. There, porting between landline, wireless and VoIP services is common, and the US and Canada carrier lookup (network.carrier_us) is the more specific option. It returns line_type and the current carrier, and runs in bulk jobs only.

A real-time request is refused. This is the real test-mode error:

{"error": {"code": "service_disabled", "status": 403, "param": "checks[0]",
  "message": "The check 'network.carrier_us' is available in bulk jobs only (POST /v1/jobs)."}}

As a job, with a US number, a Canadian number, a Dominican Republic number (also +1) and a test number with no data:

curl https://api.mobilevalidate.com/v1/jobs \
  -H "Authorization: Bearer $MOBILEVALIDATE_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: carrier-us-demo-001" \
  -d '{"numbers": ["+12025550143", "+14165550123", "+18095550100", "+447700900002"],
       "checks": ["network.carrier_us"]}'

Rows from GET /v1/jobs/{id}/results (real test-mode output, trimmed):

{"input": "+12025****43", "country": "US", "status": "completed", "attributes": {"line_type": "mobile", "carrier": "Test Carrier"}, "billed": false}
{"input": "+14165****23", "country": "CA", "status": "completed", "attributes": {"line_type": "mobile", "carrier": "Test Carrier"}, "billed": false}
{"input": "+18095****00", "country": "DO", "status": "unsupported_country", "reason": "UNSUPPORTED_COUNTRY", "billed": false}
{"input": "+44770*****02", "country": "GB", "status": "unknown", "reason": "NO_DATA", "billed": false}

The Dominican Republic number shares the +1 country code but isn't covered, so it's unsupported_country and free. Identifiers in job results are masked. Run the free POST /v1/jobs/estimate first to see the maximum cost. See bulk jobs.

#How fresh does carrier data need to be?

Fresh enough for the decision you're making. Every conclusive answer has checked_at. Keep it next to the stored carrier.

• Before a campaign or a routing change, re-check lists older than a few months. Numbers port continuously.
• Before a sensitive action, such as a password reset or a payout to a new number, check again and compare with the stored carrier. A change of carrier or line type shortly before such an action deserves a step-up.
• Repeat checks inside the freshness window can be served from your account's cache for free (cached: true, billed: false). Send max_age: 0 to force a fresh, billed check.

One limit is worth repeating. Carrier data doesn't tell you whether a number now belongs to a different person. In the US, the FCC's Reassigned Numbers Database exists for that question, so callers can avoid calling a consumer who received a number previously held by someone else.

#What are the key takeaways?

• Carrier and line type data describes the number: what kind of line it is and which network serves it now. It says nothing about the person or whether the phone is on.
• The prefix shows the allocated network. After porting, the current carrier and even the line type can differ.
• MobileValidate's carrier lookup returns line_type, carrier, original_carrier (only when it differs) and country, for every country, in real time or bulk. It's in beta because coverage varies.
• No data means unknown with NO_DATA, and it's free. Don't treat it as a fake number.
• Use carrier names as labels, not keys, and base line decisions on line_type.
• For US and Canadian lists, use the bulk-only US/CA carrier lookup. Other +1 countries come back unsupported_country at no charge.