Yes, you can use a mobile app for Two-Factor Authentication (2FA). In fact, mobile apps are one of the most popular and secure methods for implementing 2FA. Here's how it works:

1. Authentication Apps: Many online services and platforms offer the option to use authentication apps like Google Authenticator, Authy, or Microsoft Authenticator. These apps are readily available for download on your mobile device, whether it's a smartphone or tablet. Once you've installed an authentication app, you can link it to your online accounts that support 2FA.

2. Secure Code Generation: Authentication apps generate time-based one-time codes (TOTPs) that change every 30 seconds. These codes are synchronized with the service you're trying to access. When you log in, you enter the current TOTP generated by the app, providing the second factor of authentication along with your password. Since these codes are time-sensitive and generated on your device, they are considered very secure.

3. Advantages: Mobile apps for 2FA are often seen as more secure than SMS-based 2FA because they are not vulnerable to SIM swapping attacks. They also work even when your device doesn't have an internet connection, making them very reliable.

4. Backup Codes: It's essential to note that when using an authentication app, you should save or print backup codes provided by the service. These backup codes can be used in case you lose access to your mobile device or the app itself.

In summary, mobile apps for 2FA are a highly recommended and secure method to enhance the security of your online accounts. They offer the convenience of generating codes directly on your mobile device, making it a popular choice for those looking to bolster their account security.