We offer our HLR service to determine whether numbers/devices are active or not.

Firstly, please make sure to understand what an inactive phone number means in detail.

As you see in the above article, a phone could also be temporarily inactive. For example: 

  • the owner went on a long trip somewhere without reception
  • or they went abroad and switched SIM cards temporarily for the time of his trip.

Using HLR will always give you a snapshot. If you remove all inactive numbers after running one HLR, then you might include such cases and remove certain numbers who might be active again later.

So it's up to you to define a strategy, you could either:

  1. run a HLR once for your lists and remove all inactive. (the more radical but easier solution)
  2. run several HLR over a certain period of time and remove only the ones that repeatedly come up inactive. (the safer solution)


HLR cost is relatively low so you'll have a certain cost once for the determination of the number activity but might save higher SMS costs later and reduce SMS charges for repeated FAILED deliveries.

If you have any questions, please send an email to support@sms.to