Unfuddle STACK 2FA: how to set up an authenticator app

Unfuddle STACK is the original Unfuddle app, where teams keep their tickets, milestones and Git or Subversion repositories. Its two-factor authentication (2FA) is optional and uses one method: codes from an authenticator app, typed after your username and password each time you sign in (Unfuddle). Two things set it apart. STACK gives you no backup codes, and if you set up 2FA years ago through Authy, you now have to register again.

This guide uses Authenticator App - Novaz on iPhone. Any standard authenticator app works the same way.

How we checked this guide: the Unfuddle STACK steps come from Unfuddle's own help page and blog, linked below, which we read on October 24, 2026. We haven't tested them on an Unfuddle STACK account, so a label may differ slightly. The Novaz steps are checked against the app, version 1.0.5.

Moving off Authy

STACK's first 2FA system ran on the Authy service, which Twilio has since retired. If your STACK codes still come through Authy, Unfuddle asks you to register your account with an authenticator app instead. Since September 28, 2026, STACK asks you to do this before you can keep using it. Your Authy codes work until you switch (Unfuddle).

The steps are the ones below, with one difference: because your account already has 2FA, both buttons read Reset and Reconfigure. You can scan the new QR code with Novaz, or with the Authy app if you'd rather keep it, since it still works as a standard authenticator.

Turn on 2FA with an authenticator app

STACK uses standard time-based codes: 6 digits that change every 30 seconds (Unfuddle). That matches what Novaz makes, so a QR code and a typed key both work.

1. Sign in to Unfuddle STACK and open your Personal Settings page.
2. Under Two-Factor Authentication, click Setup Two-Factor Authentication.
3. Click Generate QR Code. (If 2FA is already on, these two buttons read Reset and Reconfigure.)
4. In Novaz, tap +, then Scan QR code, and point the camera at the code. If the QR code is on the same iPhone, take a screenshot, tap +, then Choose a photo. See scanning a QR code on the same iPhone.
5. If you can't scan it, click Show the Secret Key in STACK. In Novaz, tap +, then Enter key manually, type a name such as Unfuddle STACK under Service, and paste the key into Setup key. See What is a 2FA setup key?
6. Type the code Novaz shows into STACK and click Verify Code.

From then on, STACK asks for a code from Novaz every time you sign in, right after your username and password.

More than one Unfuddle account

If you belong to several Unfuddle accounts, 2FA is set up separately in each one. Repeat the steps in every account. You'll end up with one entry per account in your authenticator app, each labeled with that account's address (Unfuddle).

No backup codes

Unfuddle's help page is direct about this: "STACK does not currently issue backup or recovery codes" (Unfuddle).

The same page suggests an authenticator app that backs up or syncs codes across devices. Novaz can: turn on iCloud backup (PRO) or use Export to file… (free) in Settings › Backup. Without a backup, its keys exist only on your iPhone. Either way, keep a second fallback: another administrator on your Unfuddle account (see below). If you're the only one, consider making a trusted colleague an administrator too.

If STACK rejects your code

Unfuddle's own advice is to check that the clock on the device running your authenticator app is set automatically, because these codes depend on the correct time (Unfuddle). On iPhone, open Settings > General > Date & Time and turn on Set Automatically. Novaz also warns you when the clock is 15 seconds or more off.

With several Unfuddle accounts, check you're using the right entry. Other causes are in Authenticator code not working?

Changing phones

While you still have the old phone, sign in to STACK and use Reset and Reconfigure to register the new one (Unfuddle). Do this for each Unfuddle account you belong to. If you have a Novaz iCloud backup or backup file, you can restore your accounts on the new iPhone instead. Without one, set up each account again in Novaz on the new phone before you wipe the old one. See How to transfer your authenticator app to a new iPhone.

If you lose your authenticator

Without backup codes, recovery goes through people (Unfuddle):

• Another administrator on your Unfuddle account can turn off 2FA for you. They open your entry on the People page and choose Disable 2FA on this user. You then sign in with your password and set up 2FA again.
• If you're the only administrator, contact Unfuddle support. Unfuddle says it will verify your identity before it changes anything, but doesn't say what proof it asks for or how long it takes.

More in Lost the phone with your authenticator app?

Turning 2FA off

Go to Personal Settings, and under Two-Factor Authentication click Disable 2FA. Administrators can also turn it off for someone else from that person's page (Unfuddle). Afterwards, open the STACK entry in Novaz and tap Remove account.

Official Unfuddle help

• STACK Help - Two-Factor Authentication
• Two-Factor Authentication Update in Unfuddle STACK (Unfuddle blog, May 5, 2020)
• Unfuddle Support