One-Time Passwords have become a standard part of authentication that is available in most apps and platforms across different industries. Whether users are signing in to a banking app, confirming a transaction, resetting a password, or creating a new account, OTP verification adds a second layer of protection that makes unauthorized access harder.
But while different OTP delivery methods rely on the same concept of a temporary password, the delivery channel makes a huge difference. A code sent through an SMS is not the same as a code generated inside an authentication app. Both methods can verify users, but they differ in security, cost, reliability, scalability and user experience.
This is why the comparison between SMS OTP and app-based OTP is becoming more important for businesses building authentication flows. SMS is familiar and widely accessible, while app-based OTP offers stronger security and better long-term scalability. 
What Is SMS OTP?
SMS OTP is one of the most widely used verification methods. When a user tries to log in or complete a sensitive action, the system sends a short code via a message to their mobile number through the telecom network. The user then enters this code into the app or website to confirm their identity.
What Is App-Based OTP?
App-based OTP uses an authentication app to generate verification codes directly on the user’s device without transmission. These codes are usually time-based, which means they refresh every few seconds, often every 30 or 60 seconds. Examples of apps used to generate codes are Google Authenticator, Microsoft Authenticator and Authy.
Unlike SMS OTP, app-based OTP does not require the code to be sent through a mobile network. Once the authentication app is set up, it generates codes locally using a secure shared key between the user’s device and the service provider.
SMS OTP: The Main Advantages
The strongest advantage of SMS OTP is accessibility. Any user with a mobile number and a device that receives text messages can use it, and it has been widely used for long enough that the majority of users are used to it. 
This is especially important for businesses targeting large user bases across different regions, including users who may not be comfortable with authenticator apps or not used to them.
Another advantage is fast deployment. SMS OTP is easy to integrate using third-party providers and messaging APIs. For companies that need to launch authentication quickly, this can be a practical option, especially when security needs are moderate and the user experience must remain very simple.
SMS OTP is also useful as a backup method. Even companies that rely on app-based OTP may still keep SMS as an alternative for account recovery or users who cannot access their authenticator app.
SMS OTP: The Main Limitations
Despite its convenience, SMS OTP has clear security limitations. Because the code travels through telecom networks, it can be prone to risks that the business can never fully control. 
One of the most known risks is SIM swapping, where attackers manipulate a carrier into transferring a victim’s phone number to another SIM card. Once this happens, the attacker can receive the OTP instead of the real user.
SMS messages can also be intercepted or redirected through network vulnerabilities. While this may not happen to every user, it makes SMS less suitable for high-risk use cases such as banking, financial transactions, enterprise systems and healthcare platforms.
App-Based OTP: The Main Advantages
App-based OTP is generally stronger than SMS OTP when it comes to security. Since codes are generated locally on the user’s device, there is no message to intercept and no dependency on the telecom network. This makes it safer and more suitable in terms of security.
It is also more reliable after setup. Users do not need mobile coverage, SMS delivery or even internet access to generate the code. This is especially valuable for users who travel frequently, work in areas with weak signal or access systems from different locations.
From a business perspective, app-based OTP is also more cost-effective at scale. There are no per-message fees, which makes it suitable for platforms with large user bases or frequent authentication needs. The company may need to invest in implementation and user education, but the outcome is tangible reductions in costs. 
App-Based OTP: The Main Limitations
The main challenge with app-based OTP is user adoption and preference. Users need to install an authenticator app and complete the setup process before they can use this method, and it can be one of the longest authentication methods when it comes to initial setup.
App-based OTP also depends on the user having a compatible smartphone. This makes it less universal than SMS. If your audience includes users with basic phones, older devices, or limited app access, relying only on app-based OTP may exclude part of your user base.
There are also recovery challenges. If a user loses their phone or deletes the authentication app without backup codes, account recovery can become more complicated. Businesses using app-based OTP need to design strong recovery flows that remain secure without frustrating users.
Final Thoughts
SMS OTP and app-based OTP are both widely used authentication methods, with both having their advantages and disadvantages. We have compared the reasons to consider each, and why would you need both. And Authentica offer SMS OTP authentication.