HLR (Home Location Register) before SMS is a feature that verifies whether a recipient's number is active before the SMS is actually sent. Instead of sending to a potentially inactive number and receiving a failed delivery report, the platform first sends a silent HLR lookup to the aggregator and only forwards the SMS if the response confirms the number is reachable.
When HLR checking is enabled on a client price for a destination, the following happens for each outgoing message:
The platform sends an HLR request to the aggregator configured in the client's HLR route for that destination.
The aggregator queries the operator network and returns the current MCC and MNC for the number.
If the number is active, the platform uses the MCC and MNC from the HLR response to route the SMS to the correct operator, not the original operator assigned by prefix.
If the number is inactive, the platform does not send the SMS and immediately returns a non-delivery report to the client.
The client is not aware that an HLR is being run — it is invisible in their interface, and they are not charged separately for it. The SMS price you set for the client should account for the cost of the HLR lookup.
HLR before SMS is most useful for traffic going to MNP countries, where numbers are frequently ported between operators. Without it, the platform routes based on prefix alone, which may be incorrect for ported numbers — leading to failed delivery or billing at the wrong rate.
The main trade-off is speed: HLR checking limits sending throughput to roughly 10–50 SMS/sec. This makes it unsuitable for high-volume campaigns, but it is a good fit for transactional or time-sensitive traffic where delivery accuracy matters more than throughput.
