Live Signals
Check if a phone number is active: live status API
Telebase queries the carrier network in real time and returns whether a phone number is currently active and reachable. The active field returns true when the number is reachable on the network today, false means it is not, and null means the carrier returned data but could not confirm reachability. A single query also returns carrier, number type, country and the launching SIM swap signal. $0.03 per query, no contract.
What "active" means in the API response
An active phone number is one that is currently provisioned to a SIM card and reachable on the carrier's network. A number goes inactive when the subscription lapses, the SIM is deactivated, the number is ported away, or the account is cancelled. The check queries the carrier network directly rather than validating format alone.
The _meta.activeSource field tells you the strength of the signal:
activeSource values
- LINE_STATUS: the active field comes from a live HLR or carrier network query. The carrier has confirmed whether the number is currently reachable. This is the strong signal.
- VALID: the number passed E.164 format validation and is a plausibly real number, but the carrier did not return a reachability confirmation. The
activefield will benullin this case. Treat this as "format valid, reachability unknown" rather than "confirmed active".
When activeSource is VALID, soften any downstream logic that depends on active status. Do not treat null as false. A null active field means "we could not determine this", not "this number is inactive".
Example request and response
curl -s 'https://telebase.fatcatremote.com/api/lookup?phone=%2B447700900000' \ -H 'Authorization: Bearer tb_live_xxxxxxxxxxxxxxxxxxxxxxxx'
{
"phoneNumber": "+447700900000",
"active": true, // confirmed reachable on network
"carrier": "EE",
"country": "GB",
"numberType": "mobile",
"simSwap": "UNKNOWN",
"simSwapAt": null,
"_meta": { "activeSource": "LINE_STATUS" }
}
{
"phoneNumber": "+447700900001",
"active": null, // format valid, reachability not confirmed
"carrier": "EE",
"country": "GB",
"numberType": "mobile",
"simSwap": "UNKNOWN",
"simSwapAt": null,
"_meta": { "activeSource": "VALID" }
}
Phone numbers must be E.164 with the leading + URL-encoded as %2B. New accounts receive a $5.00 starting balance.
When active status matters for fraud and KYC
A number that fails a live reachability check at sign-up is worth flagging before a document check begins. Most legitimate customers present a number currently in service. Combined with number type detection, active status gives you a fast first filter before any expensive verification step.
Sending an OTP to an inactive number wastes cost and gives the customer a poor experience. A quick active check before dispatch reduces SMS spend and keeps conversion rates up for legitimate customers. For the SIM-specific risk at OTP, see how to detect a SIM swap before sending an OTP.
Phone numbers churn. A number that was active at sign-up may be inactive twelve months later because the customer switched operators or let the contract lapse. Batch-querying a contact list against active status identifies numbers no longer worth reaching and flags accounts that may have been abandoned.
The strongest fraud signal is a combination: inactive status plus a non-fixed VoIP type, or an inactive number from a country that does not match the applicant's stated location. No single signal is conclusive; active status is most useful as part of a multi-signal check.
Limitations of active status
Active status confirms that a number is provisioned and reachable. It does not confirm that the right person holds the SIM. A SIM swap results in an active number on the carrier's network but controlled by the wrong person. For that check, the simSwap field is the right signal. See the SIM swap detection API.
Active status also does not confirm identity. A disposable non-fixed VoIP number may be active. Active status and number type are complementary: a non-fixed VoIP number that is active is still a higher-risk onboarding signal than a mobile number that is active.