SMS VERIFICATION

Confirm user identity with an SMS verification service

One-time passcodes via SMS take the headache out of identity verification. Sinch Engage delivers OTP messages globally with the reliability your authentication flows depend on. It’s perfect for account sign-up, login verification, and right-of-use confirmation for mobile Sender IDs.

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THE WORKFLOW

How an SMS verification service works

Nobody wants their identity stolen or their account compromised. With SMS verification, you add a possession check to your authentication flow to cut down on unauthorized account access. It also supports identity-proofing requirements in authentication workflows.

How it works:

  • Your application requests verification for a phone number

  • The SMS verification service sends a one-time passcode to that number

  • The user enters the code in your application

  • Your application checks the code before completing the requested action

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COMPLIANCE BASICS

Getting SMS verification right

Using your own number means messages come from one consistent place. That makes it easier for recipients to recognize the sender and save the number.

If you send SMS messages using U.S. long codes, 10DLC registration isn’t optional. Registering helps reduce spam, protect consumers, and improve overall trust in messaging channels. Opt-out requests must be honored within two days, and complaint rates should stay below 0.1%.

WHERE IT WORKS

Common SMS verification use cases

SMS verification can help in a variety of authentication and account security workflows.

New account registration

Confirm a phone number during sign-up.

Two-factor authentication at login

Add a second step after password entry. Account security examples include 2FA, password resets, and fraud alerts.

Password and account recovery

Send a one-time passcode when a user requests account access.

Transaction confirmation

Request a one-time passcode before processing payments or other high-value actions.

Re-verification after inactivity

Ask the user to verify again after a period of inactivity.

CAPABILITIES

Core capabilities and requirements

One-time passcodes (OTP) by SMS

An SMS verification service sends a one-time passcode to a user’s phone number. Your application uses it to confirm control of that number.

Sender ID consistency

Using your own number means messages are sent from a single, consistent number. Recipients can recognize the sender and save the number.

10DLC registration for U.S. long codes

If you send SMS using U.S. long codes, 10DLC registration is essential. Your brand is registered, campaign use cases are declared, and long code numbers link to a registered campaign.

Mobile number verification for Sender ID

You need access to the mobile device for that number. A verification code is sent to the selected number, and you enter that code to confirm right of use.

Re-verification every 12 months

You need to re-verify the number every 12 months.

Opt-out and complaint-rate expectations

Opt-out requests must be honored within two days. Complaint rates should stay below 0.1%.

FAQs

Frequently asked questions about SMS verification

An SMS verification service sends a one-time passcode (OTP) via text message to a user’s mobile phone number. Your application uses it to confirm the user controls that number.

Your application requests verification for a phone number. The SMS verification service sends a one-time passcode by SMS, and your application checks the code the user enters.

Common SMS verification service use cases include new-account registration, two-factor authentication at login, and password resets. They can also include transaction confirmation and re-verification after inactivity.

Using your own number means all messages are sent from a single, consistent number. That makes it easier for recipients to recognize who the message is from and save the number for future reference.

10DLC stands for 10-digit long code. If you send SMS messages using U.S. long codes, 10DLC registration isn’t optional — it’s essential.

Typically, accounts are verified in 1–2 hours. During high-demand periods, verification can take up to 24 hours.

Opt-out handling requires honoring unsubscribe requests within two days. Complaint rates should stay below 0.1%. Registration is intended to reduce spam, protect consumers, and improve overall trust in messaging channels.

Yes, in supported countries. You need access to the mobile device for that number so you can verify right of use, and you re-verify every 12 months.

Supported countries include Australia, Austria, Croatia, Cyprus, Denmark, Estonia, Finland, Germany, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Norway, Portugal, Slovenia, Spain, Sweden, Switzerland, the Netherlands, and the United Kingdom.

If you’re sending SMS messages using U.S. long codes, 10DLC registration is essential. Unregistered messages can face filtering and delivery restrictions.