What is SMS Verification & How Does It Work?

June 13, 2024
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Alvin Lee
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What is SMS Verification & How Does It Work?

In 2022, over 24 billion sets of usernames and passwords were put up for sale on the dark web. Meanwhile, IBM reported a 71% increase from 2022 to 2023 in cyberattacks that used stolen or compromised credentials.

But don't panic. That's why we verify with SMS. For those who don’t know, SMS just means texting. You can secure accounts instantly on your mobile phone through text message verification.

Passwords can be relatively easy to steal. LastPass reports that 62% of people always or mostly use the same password or a variation. Phones are a lot harder to steal. If your phone happens to be lost or stolen, but you have SMS verification enabled, then you make a hacker’s job significantly harder. To compromise your account, a hacker would need your username, password, and access to your phone (and they might even need a password to unlock your phone).

That's a lot of protection for your data—and with everything you keep online, security is essential.

So what exactly is SMS verification, and how does it work? And how can you offer it to your customers? That’s what we’ll cover in this post.

What is SMS verification?

SMS text verification lets websites, apps, banks, and social networks double-check a user’s identity.

After entering your username and password, you’ll receive a text message with an SMS verification number on your smartphone. Use that number to complete your login. That’s SMS verification.

SMS verification goes by other names too:

SMS authentication to your mobile phone isn’t a silver bullet. There are still some security risks and costs to consider (which we cover below). However, its convenience and effectiveness make it a worthwhile approach for protecting your customers and their data. Plus, most modern consumers have gotten used to this kind of verification over the years since it doesn't require any additional apps or services.

How does SMS verification work?

SMS verification is fairly straightforward. Here are the steps:

  1. Provide your phone number to a business during the account sign-up process (in addition to setting up a username and password).
  2. Enter your username and password on the business' website or app to receive a one-time text verification number.
  3. The site sends a one-time text verification (typically a six-digit code) to your phone number.
  4. Type that code into the app or website to complete the login process.

It's that straightforward. Give your phone number, get an SMS verification number, and sign on. This extra step of verification provides your account with significant additional protection from being hacked.

Pros of SMS authentication

SMS authentication offers many benefits:

  • Security: While mobile SMS verification isn't as secure as other modern-day alternatives, such as time-based one-time passwords (TOTP), it’s still more secure than a password alone.
  • Familiarity: Many people are familiar with the process of entering a verification code received via SMS, making it a user-friendly option.
  • Affordability: Implementing SMS 2FA is inexpensive. Users don’t need to install an app or get any additional hardware for their mobile phones.

Cons of SMS authentication

While SMS verification is secure and affordable, there are a few potential cons:

  • Security vulnerabilities: SIM swapping (fraud) can compromise an account Luckily, our Lookup SIM Swap can save the day.
  • Lost devices: People lose their devices all the time, which could keep them locked out and/or compromise their security. This is also a security threat if the device is found or stolen by others.
  • Synced devices: Many people receive their text messages on multiple devices (such as their mobile phone, smartwatch, or computer). This makes it easier for bad actors to intercept a customer’s SMS verification number.

Who uses SMS verification?

Companies from a wide range of industries—like banking, healthcare, social media, and retail— frequently use SMS verification to confirm a user’s identity. It's become a typical security feature found on both websites and mobile apps.

On the flip side, if you’re a consumer with an account for any of these services, then you're probably familiar with SMS verification. All it takes is receiving a text verificaton code and using it to sign in.

This method is popular because it's simple. It only requires a phone that can receive texts.

How to choose an SMS verification service

With so many SMS text verification services, how do you find the right one for your business? Here are a few things to look for:

  • Speed and reliability: Look for a service that delivers verification codes quickly and reliably, especially since users typically have only minutes to enter the code before it expires.
  • Scalability: If you’re sending thousands of SMS 2FA messages to customers, then you’ll need a service that can match your scale without sacrificing speed.
  • Security: Mobile SMS verification messages need to be secure. If not, attackers can intercept unprotected messages and use the code to gain access to your users’ accounts. Work with a verification service that's SOC 2 compliant (the gold standard for data security).
  • Top-notch support: When something goes wrong, you need a service provider that can assist immediately.
  • Alternate verification options: Some users might not want to use their mobile phone for verification, and that's fine. Choose a provider with other 2FA options, such as email, push, or TOTP.

Secure SMS two-factor authentication with Twilio Verify

Want an SMS verification service that checks all the boxes? Try secure 2FA from Twilio Verify.

Yes, we know we're a bit biased, but hear us out.

Verify lets you validate your users with SMS, voice, email, push, and TOTP all within a single API. 

You can integrate the Verify API into your sign-up flow to capture (and confirm) phone numbers during the customer onboarding process. This makes security a priority while maintaining a smooth user experience.

You can also use carrier-approved, templated messages to ensure your SMS verification numbers don't get tied up in the message filters. What's more, you can send messages globally without any hiccups, thanks to Twilio's automatic translation and global regulations compliance.

Want to learn more? Check out our Twilio Verify API page for all the details.

How to get started with an SMS verification API

Ready to get started with an SMS text verification API? Check out our code samples and follow a three-step process:

Step 1: Choose a language

The Twilio Verify API offers a quickstart for SMS verification in the following programming languages/frameworks:

  • Ruby
  • Python
  • .NET
  • JavaScript
  • PHP
  • Java

Step 2: Obtain an API key. If you don’t have an API key, get one for free here.

Step 3: Set up the code sample. Follow the setup instructions for the project in the language you’ve selected. Typically, this involves:

  1. Downloading the quickstart code

  2. Configuring the application with your Twilio account information

  3. Running a script to build the application

  4. Deploying the application locally or to the cloud for testing

Alternatives to SMS verification

While SMS verification is popular, alternative verification methods can also provide enhanced security and convenience. These include:

  • WhatsApp: Send verification codes via WhatsApp, which can be more convenient for users who regularly use this messaging platform.

  • Push and silent device approval: Users can authenticate via push notifications sent to their devices, which can be approved silently without entering a code.

  • TOTP: The user generates a time-based temporary code in an authenticator app, which matches your system’s generated code at that exact moment.

  • Email: Send verification codes directly to a user's email address as a secure alternative to SMS.

  • Voice: Use voice calls to deliver verification codes. This is particularly useful for users who have accessibility needs or do not have reliable text message service.

Find more SMS verification resources

Through the Verify API, Twilio offers a variety of tools to help you with SMS verification. Within a single API, your company can enable verification across multiple channels, dramatically improving security for your customers’ accounts—efficiently and at scale.

To learn more about how Twilio Verify can help, check out the following resources:

Want to learn more about what you can do with SMS? Check out our guide to SMS Marketing for Beginners. Then, when you’re ready, you can get started for free.