What it is
HLR stands for Home Location Register, a core database inside every mobile network that tracks subscriber information. An HLR lookup queries that database in real time to check whether a given phone number is active, which network it sits on, and whether it has been ported.
For a lead generator, that tells you before the lead leaves your system whether you are sending a buyer someone they can reach or a dead number.
How it works
When you run an HLR lookup, your provider sends a signalling message (over SS7 or Diameter) to the mobile network that owns the number. The network's HLR responds with the subscriber's current status. The round trip typically takes one to three seconds.
No call or text is involved. The lookup happens at network level and the subscriber never knows it took place.
What an HLR lookup returns
A standard lookup returns four fields, which between them tell you far more about a number than a format check can.
Active / inactive status
Is this number currently connected to a network and able to receive calls and texts? This is the field that matters most. If a number is inactive or decommissioned, there is no point sending it to a buyer.
Network / operator
Which mobile network the number currently belongs to. Useful if your buyers have preferences or restrictions around certain carriers.
Ported status
Whether the number has been moved from one network to another. A number that starts with an O2 prefix but is now on EE has been ported. This affects routing and can flag numbers that have changed hands.
Roaming
Whether the device is currently registered on a foreign network. A roaming UK number might not be in-market for a UK-focused buyer.
Why it matters for lead generation
Buyers pay for contactable leads. If you send a lead with a disconnected number, the buyer cannot reach them, and you can expect a return or a clawback, plus a buyer who trusts your leads a little less. HLR lookups catch dead numbers before they reach a buyer.
If 5% of your leads have dead phone numbers and your average lead price is five pounds, uncontactable numbers are costing you 25p on every lead you send. Compare that with what your provider charges per lookup to see whether the check pays for itself.
Beyond dead numbers, HLR data helps with quality scoring. A number that is active, on a UK network, and not roaming is a stronger signal than one that passes format validation alone. Some operators use HLR results as a filter, routing only confirmed-active numbers to premium buyers.
HLR vs basic validation
Format validation tells you a number looks correct; HLR tells you it is live on a network right now. Run both, with the format check first.
Format validation
- Checks number length and format
- Validates country code prefix
- Instant, no external call
- Free
- Cannot tell if the number is live
HLR lookup
- Queries the mobile network itself
- Confirms number is live and active
- Returns network, porting, roaming
- 1 to 3 second response time
- Charged per lookup
Run format validation first. It catches obvious junk (too few digits, landline prefixes, non-numeric characters) instantly and for free, and HLR then checks the numbers that pass. Paying for a lookup on a malformed number is wasted money.
How it works in Hawfinch
Hawfinch runs HLR lookups through a specialist HLR provider. A lookup returns the number's live status, its network and its line type. Hawfinch does not report ported or roaming status.
HLR is switched on per buyer link, not per campaign. It runs during distribution, just before that buyer would be sent the lead, not when the lead first arrives at the API. If the result is DEAD, NOT_APPLICABLE or BAD_FORMAT, that buyer is skipped and the lead falls through to the next buyer in the waterfall. ABSENT_SUBSCRIBER, meaning the phone is switched off or out of coverage, is accepted unless you turn off "accept absent" for that buyer. A lookup error or an INCONCLUSIVE result never rejects a lead.
Lookups run live when a lead is routed. If HLR already ran on a lead when its CSV was imported, that result is used. You can also run HLR on a CSV when you import it, or check a list of numbers in Files. HLR is charged per lookup on every plan.