Glossary
What is an HLR lookup?
An HLR lookup asks a mobile network's Home Location Register about a cell number: is it an active subscriber, which network holds it, and, on some networks, whether the phone is reachable or roaming. It only works for mobile numbers.
The terms behind an HLR lookup
| HLR | Home Location Register. The central database in a GSM / 3G mobile network that holds the record for each subscriber of that network. |
| MSISDN | The phone number itself, in international format. This is what you send in an HLR lookup. |
| IMSI | The subscriber identity stored on the SIM card. The HLR links each MSISDN to an IMSI. |
| MSC / VLR | The switching center and visitor register currently serving the phone. The HLR keeps track of which one that is, which is how it knows if the phone is reachable or roaming. |
| HSS / UDM | The databases that play the HLR role in 4G (HSS) and 5G (UDM) networks. |
How an HLR lookup works
Every mobile subscriber has a record in the home network's HLR (or its 4G and 5G successors). When a call or text is routed to a cell phone, the network asks the HLR where the subscriber is. An HLR lookup service sends that same kind of query over the mobile signaling network (SS7) without placing a call, and reports back what the network answered.
What comes back depends on the network and the provider. Some networks return detailed status; others return little or block the query. That is why results vary between countries and carriers.
Limits of HLR lookups for US lead lists
- Mobile only: landlines and most VoIP numbers have no HLR record, so a mixed lead list needs a line type check anyway.
- Network dependent: the detail you get depends on what each mobile network answers.
- Not a compliance check: an HLR result says nothing about Do Not Call status or consent.
HLR lookup vs. TrueSearch line type check
| HLR lookup | TrueSearch | |
|---|---|---|
| Works on | Mobile numbers only | Mobile, landline, VoIP and toll-free numbers |
| Line type | Mobile by definition | Mobile, landline, VoIP or toll-free |
| Carrier | Home network, depending on the provider | Carrier name for every number |
| Live handset status | Can indicate whether the phone is reachable or roaming, depending on the network | No. Returns valid or dead (disconnected / not assigned), not whether the handset is switched on |
| Bulk lists | Depends on the provider | CSV or Excel upload, about 30 seconds per 1,000 numbers |
What TrueSearch returns, and does not
| Valid or dead (disconnected / not assigned) | Yes, every number |
| Line type: mobile, landline, VoIP, toll-free | Yes, every number |
| Carrier name | Yes, every number |
| Bulk upload (CSV or Excel) | Yes, results in about 30 seconds per 1,000 numbers |
| REST API | Yes (JSON, one API key) |
| Claude / ChatGPT / Cursor connector (MCP) | Yes |
| National or state Do Not Call check | No, not yet |
| Known TCPA litigator check | No, not yet |
| FCC Reassigned Numbers Database check | No |
| Starting price | $97/month for 5,000 numbers, 7-day free trial |
| One-off list | $20 per 1,000 numbers, no subscription |
Upload a CSV or Excel file. Every number comes back valid or dead, mobile, landline, VoIP or toll-free, with carrier.
Starter: $97/month for 5,000 numbers after the 7-day trial. Cancel anytime.
Questions
What is an HLR lookup?
An HLR lookup is a query sent through the mobile signaling network to the Home Location Register of the network that holds a cell number. Depending on the network and the provider, it can tell you whether the number is an active subscriber, which network it belongs to, whether it has been ported and whether the phone is roaming.
What does HLR stand for?
Home Location Register. It is the subscriber database in GSM and 3G mobile networks. In 4G the same role is played by the HSS (Home Subscriber Server) and in 5G by the UDM (Unified Data Management).
Can an HLR lookup check landlines or VoIP numbers?
No. Landline and most VoIP numbers are not mobile subscribers, so there is no HLR record to query. To tell mobile, landline and VoIP numbers apart you need a line type lookup.
Is an HLR lookup the same as a carrier lookup?
Not exactly. A carrier lookup returns who currently holds the number and what kind of line it is, and works on any US number. An HLR lookup goes to the mobile network itself and can add live status for cell numbers, but only covers mobile numbers and what each network chooses to answer.
Does TrueSearch do HLR lookups?
TrueSearch does not market itself as an HLR lookup. For every number it returns valid or dead, line type (mobile, landline, VoIP or toll-free) and carrier from carrier data, by CSV upload or REST API. It does not report whether a handset is switched on or roaming.
Does TrueSearch check Do Not Call status?
No. TrueSearch checks validity, line type and carrier only. For Do Not Call status, use the National Do Not Call Registry at donotcall.gov.
Related: what is phone line type?, free carrier lookup, HLR Lookups alternative, landline checker and VoIP number detection.
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This guide is general information, not legal advice. TrueSearch for Business checks validity, line type and carrier from licensed telecom data. It does not check the National Do Not Call Registry, state DNC lists or the FCC Reassigned Numbers Database. Not a consumer reporting agency; not for FCRA purposes.