In Nextcloud, there is the option to set up Two Factor Authentication. The steps you have to follow in order to use it are the following:

  1. Install TOTP app on Nextcloud.
  2. Enable TOTP on Personal Settings, under TOTP second-factor auth section. A QR code will show up.
  3. Install andOTP on your android phone (you can use any TOTP client you want, andOTP is available in F-droid)
  4. Scan the QR code that is shown in step 2 with andOTP.
  5. andOTP and Nextcloud are merged and now every 30 seconds a new TOTP password is generated.

Now when you log in you will be prompted, in a second step, to type a TOTP password. Type the password shown in the andOTP app.

App Passwords

You must add App Passwords to generate a password for every app that needs access to your Nextcloud account.
Example: Nextcloud Desktop / Mobile Client, DavDroid app, Notes App (Mobile), etc.

To add an App Password do the following.

  1. Navigate to Personal settings, under Settings section (here you will see every application that has access to your Nextcloud Account). Scroll until you find App passwords.
  2. Fill in the box that says App name with the application’s name that you want to use (use a name that is convenient and it is distinguished from other apps).
  3. An Application Password is now generated and displayed in a gray box. Type this password (and the your username) on the application you want to use. After you log in hit Done.

Note: After you type Done, the password will never be revealed again. You may want to use a password manager to save this password, or create a new App Password every time you loose a password