VLR (Visitor Location Register), is a key component in the 2G/3G mobile circuit-switched (CS) network architecture. It coexists with the MSC server.

It is responsible for maintaining and managing information about mobile subscribers who are temporarily located within the coverage area of a specific MSC server.

When a mobile subscriber roams into a new geographical area, their device registers with the local VLR. So that it stores the subscriber's current location information. Then it tracks the subscriber's location within its own service area, enabling efficient call routing and delivery of services.

The VLR communicates with the HLR to obtain subscriber information, and to inform the HLR that it currently serves this subscriber.