Landline SMS lookup

Landline SMS lookup: find the landlines that can receive texts

Q: Do I still get the voice carrier?

Yes. The voice carrier comes from the live carrier dip (dipCarrier) on every lookup. The messaging provider is a separate field (dipMessagingProvider).

The CheckThatPhone landline SMS lookup checks whether a US or Canadian landline is enabled for text messaging and, if it is, which messaging provider serves it. About 7% of landlines we check are SMS-capable.

Turn it on with landlineSmsLookup: true. It costs one extra credit, charged only when the number is a landline. Without it, a landline is never marked SMS-eligible, so text-enabled landlines get filtered out with the rest.

Get a free API key Landline SMS fields in the docs →

How the check works

Add "landlineSmsLookup": true to a POST /v1/lookup request, or tick "Landline SMS lookup" on a bulk CSV upload.
We run the normal lookup, including the live carrier dip. If the number is a landline, we also run the messaging lookup.
Mobile numbers skip the check: the dipMessaging* fields are left out and the extra credit isn't charged.
For an SMS-capable landline, dipMessagingEnabled is "true", the provider fields are filled in, and smsEligible comes back "true".

The five dipMessaging fields

Field	Example	Meaning
`dipMessagingLookup`	`"true"`	Present only when `landlineSmsLookup: true` is set and the lookup actually ran, i.e. the number is a landline: `"true"`. Absent for mobile numbers (the lookup does not apply and is not charged) and when the add-on is not requested.
`dipMessagingEnabled`	`"false"`	Returned only when `landlineSmsLookup: true` is set. `"true"` if landline messaging is enabled for this number. Only meaningful alongside `dipMessagingLookup: "true"`.
`dipMessagingProvider`	`"Google (Grand Central) - SVR"`	Name of the messaging provider serving this landline number. Populated only when the landline messaging lookup returned a positive match.
`dipMessagingRefId`	`"us_acme"`	Messaging provider's reference ID for this number.
`dipMessagingCountryCode`	`"US"`	Two-letter country code of the messaging provider.

The base field smsEligible is "true" for an active mobile, or for a landline this check confirmed as SMS-capable. Its inverse, doNotSms, marks numbers that can't take a text.

Example request and response

curl --request POST \
  --url 'https://api.checkthatphone.com/v1/lookup' \
  --header 'Authorization: Bearer YOUR_API_KEY' \
  --header 'Content-Type: application/json' \
  --data '{"phone": "(415) 555-0176", "landlineSmsLookup": true}'

A response excerpt for a text-enabled landline (illustrative: a fictional 555 number, with the carrier, deliverability and location fields left out for space):

{
  "success": true,
  "credits_used": 2,
  "data": {
    "subscriber": "4155550176",
    "dip": "success",
    "dipCarrierType": "landline",
    "dipMessagingLookup": "true",
    "dipMessagingEnabled": "true",
    "dipMessagingProvider": "Google (Grand Central) - SVR",
    "dipMessagingRefId": "us_acme",
    "dipMessagingCountryCode": "US",
    "smsEligible": "true",
    "error": "false"
  }
}

credits_used: 2 is one credit for the lookup and one for the landline SMS check. The same request for a mobile number would show credits_used: 1 and no dipMessaging* fields.

Routing on the result

Mobile (dipCarrierType: "mobile"): text as usual.
Landline with dipMessagingEnabled: "true": SMS-capable; it can go on the SMS list.
Landline with dipMessagingEnabled: "false": not SMS-capable. Route it to a voice queue or leave it out of the SMS send.

Being able to receive a text is not the same as consent to receive one. Your consent records still decide who you can message, and the TCPA litigator scrub can run in the same call.

Pricing

The landline SMS lookup adds one credit per lookup, only when the number is a landline. Mobile numbers pay the base credit and nothing more. For example, on a 10,000-number list where 2,000 numbers are landlines, the add-on adds 2,000 credits, for 12,000 credits in total.

The Free plan includes 500 credits a month and paid plans start at $5 a month. See pricing for every plan and overage rate.

Landline SMS lookup: common questions

What is a text-enabled landline?

A landline number with messaging enabled through a messaging provider, so it can receive SMS while voice calls still go to the landline. The lookup reports whether that is the case (dipMessagingEnabled) and which provider handles the texts (dipMessagingProvider).

How many landlines can receive SMS?

About 7% of the landlines we check are SMS-capable. Without the check, those numbers look like any other landline.

Am I charged for mobile numbers?

No. The check only runs on landlines. For a mobile number the dipMessaging* fields are left out and no extra credit is charged.

Does it work on a whole list?

Yes. Tick "Landline SMS lookup" when you upload a CSV from the dashboard; the result file then includes the five dipMessaging* columns. See bulk phone validation.

Do I still get the voice carrier?

Yes. The voice carrier comes from the live carrier dip (dipCarrier) on every lookup. The messaging provider is a separate field (dipMessagingProvider).

Field reference: Landline SMS Lookup in the docs
Line types first: Line type lookup API (mobile, landline, VoIP)
Channel routing: Sales lead validation and routing
Background: Landline SMS: how text-to-landline routing actually works
Background: Why your SMS campaign is silently dropping landlines