Fundamentals BroadNet answer

What is an HLR (Home Location Register)?

Last reviewed September 30, 20261 min readReviewed by BroadNet engineering

Quick answer

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.

Plain-language definitionVendor-neutralReviewed September 30, 2026

The long answer

Everything worth knowing, nothing that isn't.

§01

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.

§02

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.

BNWritten by the BroadNet engineering team·Operating carrier-grade messaging since 2003, headquartered in Dubai·Editorial standards

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