When a signup form captures a phone number, there are two questions we can answer that cost very different amounts of credits: does this number have a valid format? (1 credit, instant) and is the line on and reachable right now? (6 credits, 2-10 seconds, real-time query to the mobile network). Choosing wrong overpays or lets real leads slip.
What local validation does
Local validation normalizes the number to E.164 and compares it against the country's numbering rules. It returns country, estimated line type, suspicious patterns (repeated digits, keypad) and a basic quality verdict. It queries nothing externally — everything resolves against local datasets.
- Typical latency: < 50 ms.
- Cost: 1 credit (≈ USD 0.0045 on the M pack).
- Useful for: validating formats in real-time forms.
- Does not help with: knowing if the line exists on a real network or is active.
What carrier lookup (Telnyx) does
A middle tier. It asks the industry (via Telnyx) who the real carrier is, whether the number is ported from the original carrier, and confirms whether it is mobile, landline or real VoIP. Returns carrier, portability and a 0-100 quality score noticeably stronger than local.
- Typical latency: < 300 ms.
- Cost: 3 credits.
- Useful for: lead scoring before passing to the sales team.
- Does not help with: knowing if the line is active right now.
What live line (HLR) does
The most expensive tier. Makes a real HLR (Home Location Register) query to the mobile network, the same registry a network consults to decide which cell to route a call to. Returns connected,absent or unknown, plus portability and international roaming detail.
- Typical latency: 2-10 seconds — because it actually queries the network.
- Cost: 6 credits (on top of the tier you picked).
- Useful for: before calling or sending volume SMS/WhatsApp.
- Does not help with: landlines or VoIP — those return the type and are not charged.
When to use each
The practical rule: when saving a lead, use local (cheap junk filter). When about to make a commercial decision on the lead (handing to a rep, sending an offer), use carrier so the score is solid. When about to attempt a real contact (call, SMS, WhatsApp), use HLR to avoid wasting the attempt on a switched-off number.
In a typical B2B call center, the pattern that balances the equation is: local at signup → carrier when the lead reaches "qualified" → HLR right before the first contact attempt. 10 credits spread across the funnel beat spending 6 on every form submission.
What to do when the phone is off
A number returning absent is not a fake number: it is an off or out-of-coverage device now. Query again in an hour or before the next attempt. If you repeat within minutes our cache returns the previous result (charged the same) with the last-check timestamp, so you can decide whether a refresh is needed.