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# HLR lookup: check if a phone is switched on and reachable

An HLR lookup queries the subscriber register a number is registered against, so it answers whether a handset is switched on and reachable right now. That is a different question from whether a number is well formed. Use it before sending SMS, or to clean a list of numbers that no longer belong to anyone.

## What it tells you

- The live network status in the carrier's own wording: connected (registered and reachable), absent (assigned, but the handset is off or out of coverage), invalid (not assigned to a subscriber) or undetermined (the network did not answer).
- Whether the handset is roaming.
- The carrier the number sits on, including its network codes.
- The country the number belongs to.
- A suggested next action.

## What you need to provide

The phone number you want to look up. International format (E.164) is strongly recommended.

## What it costs

5 credits per lookup. Live per-product costs are shown on the Billing page in your dashboard.

## How to run it

- In the dashboard: HLR Status Check
- From your code: POST /v1/hlr-lookup, then see the Developer Hub at app.1lookup.io/developer-hub.

## Good to know

- Score on the network status field, not on the convenience valid flag. That flag is false only for a number not assigned to a subscriber, so both absent and undetermined read as valid.
- A lookup that comes back as not assigned to a subscriber is not charged.
- Results are point-in-time. This is a live check at the moment you run it, so a handset that is off now can be reachable an hour later: treat absent as a retry signal rather than a dead number.
- Undetermined means the network did not answer, not that the number is bad. Run it again later before acting on it.