# What is an HLR (Home Location Register)?

> The HLR (Home Location Register) is the central subscriber database in a 2G/3G mobile network. It stores each subscriber's MSISDN, IMSI, service entitlements, and the address of the MSC/VLR currently serving them. When an SMS arrives, the destination operator's SMSC queries the HLR over SS7 MAP (SendRoutingInfoForSM) to locate the subscriber before delivery. In 4G/5G the HSS — and later the 5G UDM — replaces it. The HLR is the network element itself; querying it from outside the operator is a separate service, HLR Lookup — see /answers/what-is-hlr-lookup.

- Canonical URL: https://www.broadnet.me/answers/what-is-hlr
- Language: en
- Last reviewed: 2026-09-30
- Publisher: BroadNet (https://www.broadnet.me)

## HLR vs VLR vs HSS

The HLR is the permanent system of record for a subscriber's home network. The VLR is a temporary working copy held by whichever MSC currently serves the handset. The HSS (Home Subscriber Server) is the 4G Diameter-based successor to the HLR. See /answers/what-is-vlr, /answers/what-is-msc, and /answers/diameter-s6a-explained.

## Why the HLR matters for deliverability

A live query against the HLR reveals whether a number is active, which operator currently owns it (crucial after number porting), and whether the subscriber is roaming. Exposed as a standalone API this is HLR Lookup — the single most useful list-quality check before an A2P send. See /products/hlr-lookup and /answers/what-is-hlr-lookup.

## Related

- [All answers](https://www.broadnet.me/answers)
- [Glossary](https://www.broadnet.me/answers)
- [What is HLR Lookup?](https://www.broadnet.me/answers/what-is-hlr-lookup)
- [What is an MSRN (Mobile Station Roaming Number)?](https://www.broadnet.me/answers/what-is-msrn)
- [What is a VLR (Visitor Location Register)?](https://www.broadnet.me/answers/what-is-vlr)
- [What is an MSC (Mobile Switching Centre)?](https://www.broadnet.me/answers/what-is-msc)
- [SS7 MAP — what it is and why messaging still depends on it](https://www.broadnet.me/answers/ss7-map-explained)
- [What is MNP (Mobile Number Portability)?](https://www.broadnet.me/answers/what-is-mnp)
- [HLR Lookup](https://www.broadnet.me/products/hlr-lookup)