Number Validation (US only)

Number Validation lets you verify whether phone numbers on your contact list are active, reachable, and capable of receiving SMS - before you send a single message. This helps you reduce wasted spend, protect your sender reputation, and stay compliant with carrier regulations.

Where to find Number Validation

Number Validation lives under the Contacts menu in the left-hand navigation.

If any of your recent campaigns had failed messages sent to landlines or VoIP numbers, you will also see a banner notification on your All Contacts page and in campaign reports, prompting you to check your list. You can click the banner to go directly to the Number Validation page.

From the Number Validation page, you can:

• Validate a file (bulk upload)
• Validate a single contact number

Validate a file (bulk)

Use this option to check a list of phone numbers in bulk. The experience is similar to importing a contact list. To correctly prepare your import file, follow the detailed instructions. 

1. Navigate to Contacts > Number Validation.
2. Select Validate a file.
3. Drop your CSV file or click to upload it.
4. Map the phone number column to the correct field, then click Import.

5. You'll see a summary of your numbers broken down by deliverability status - including how many can receive SMS, can't receive SMS, or are unlikely to receive - along with a billing breakdown and the option to unlock results and unsubscribe invalid contacts in one click.

What you see after unlocking the results:

• The line type for each number: mobile, landline, VoIP, or unknown
• The carrier associated with each number
• Whether each number can or cannot receive SMS
• The cost charged for validating your list (charged per lookup)

Validate a single contact

You can also validate a single phone number at any time.

1. Navigate to Contacts > Number Validation.
2. Select Validate a single contact.
3. Enter the phone number and click Validate.
4. The result will show the line type and carrier.

Review results and unsubscribe invalid numbers

After validation, you can filter results by line type to isolate numbers that cannot receive SMS (landlines and VoIP).

You have two options for handling invalid numbers:

• Unsubscribe during unlock: When you unlock your results, you can opt to unsubscribe invalid numbers in the same step.
• Unsubscribe after the fact: Use the filters on the results page to find non-SMS-capable numbers, then unsubscribe them manually.

View your validation history

All past validation sessions are saved under the History tab on the Number Validation page. From here you can:

• See how many numbers could and could not receive SMS
• Review the cost of each validation session
• Re-examine results and take further action on any numbers

Frequently asked questions

What is number validation?

Number validation checks whether a phone number is active, reachable, and capable of receiving SMS. It identifies the line type (mobile, landline, VoIP, or unknown) and the current carrier, so you know the quality of your contact list before you send.

Can it detect landlines?

Yes. Every number is classified as mobile, landline, VoIP, or unknown. You can use this information to filter out numbers that cannot receive SMS, avoiding wasted spend on undeliverable messages.

Does it cost extra?

Yes. Validation is charged at a per lookup rate, on top of your existing plan. You only pay for the lookups you run.

How often should I validate my list?

We recommend validating new contacts at the point of import. For existing lists, a periodic refresh is good practice - especially if your list has not been updated in a while or you are seeing higher than usual failed message rates.

Is number validation available outside the US?

Number validation is currently available for US customers only.

Why does this matter for compliance?

Sending SMS to landlines without proper consent can expose your business to TCPA violations, which carry fines of $500–$1,500 per incident. Validating your list before sending reduces this risk.