Split key and shield failing to open a lock
If your two-factor (2FA) step works in Safari or Chrome but fails in Firefox on iPhone (code rejected, approval page won’t load, or you get kicked back to sign-in), it’s usually a browser-specific cookie/tracking or “hand-off” problem—not your account.

Let’s fix Firefox first, without weakening your security more than necessary.

Before you start: keep Firefox open on the 2FA screen while you try each step. Many sites invalidate a code if the session changes.

1. Confirm it’s a Firefox-only issue (quick control test)

This sounds obvious, but it saves time: you want to know whether you’re dealing with an account lockout/rate limit, or a Firefox session problem.

  • Try the same login + 2FA flow in Safari (or Chrome) on the same iPhone and the same network.
  • If Safari/Chrome works but Firefox fails, continue below (this article is for that case).
  • If all browsers fail, stop troubleshooting the browser and check account status, time/date, or “too many attempts” blocks.

Cookie and shield with a privacy toggle switch
Firefox’s privacy tools can block the exact cookies some 2FA flows require.

2. Temporarily relax Enhanced Tracking Protection for the login site

Many modern sign-ins and 2FA steps rely on cross-site redirects and cookies (especially when an identity suggests “Continue with…” or uses an embedded challenge/approval step).

In Firefox on iOS, try this just for the site you’re logging into:

  • Open the login page in Firefox.
  • Tap the menu (usually the three dots) and find Tracking Protection / Enhanced Tracking Protection.
  • Turn protection off for this site (or set it to a less strict mode), then reload and try the 2FA step again.

If it works, you can keep protection off only for that site (safer than changing global settings).

3. Allow cookies for the sign-in flow (common Firefox vs Safari difference)

When 2FA “works elsewhere,” the failure in Firefox is often that a required cookie never sticks during the redirect between the service and its identity provider.

What to try:

  • In Firefox settings, look for Cookies / Tracking controls and ensure cookies aren’t blocked too aggressively.
  • If there’s an option related to blocking cross-site tracking/cookies, try loosening it temporarily while you complete sign-in.
  • After changing the setting, fully reload the login page and attempt 2FA again.

Tip: if the site uses “Sign in with Google/Apple/Microsoft,” it’s especially sensitive to cross-site cookie handling.

4. Clear site data for only the problem site (avoid a full wipe first)

Safari and Chrome can succeed because they don’t have the same corrupted/stale session cookie that Firefox is holding onto.

Try a targeted reset:

  • In Firefox iOS settings, find the option to clear Website Data / Site Data (or manage data per site if available).
  • Clear data for the specific domain(s) involved in the sign-in (the main site and any identity domain you see during redirects).
  • Restart Firefox and try again.

If you only see an “all data” option, consider Step 5 first to avoid losing too much.

Broken redirect chain link near a secure lock
A failing 2FA page is often a broken redirect chain (blocked cookie, blocked script, or a stuck session).

5. Try a clean session: Private tab (and disable content blockers for a minute)

A private session removes most “sticky” state. It’s a quick way to confirm whether cached data, extensions, or blockers are the issue.

  • Open a Private tab in Firefox.
  • Navigate to the login page again (don’t reuse the old tab).
  • If you use any iOS content blockers (system-level), temporarily disable them and retry the 2FA step.

If it works in Private mode, go back and clear site data (Step 4) or adjust tracking/cookie settings (Steps 2–3) so normal tabs work again.

6. Fix code “rejected” problems: check time, keyboard autofill, and copy/paste

If the page loads but the code keeps being rejected in Firefox (while Safari accepts it), it’s often not the code—it’s the input or timing.

  • Check iPhone time: Settings > General > Date & Time > enable Set Automatically. Time drift breaks authenticator codes.
  • Type the code manually once: Some sites are picky if a copied code includes a hidden space.
  • Watch for “old tab” codes: If you request a new code, the prior one may be invalidated immediately.
  • Avoid switching apps too long: If Firefox reloads the page when you return, the session may change and the code won’t match.

Final thoughts

When 2FA behaves differently between Safari/Chrome and Firefox on iOS, it’s usually privacy/cookie controls or stale site data—not a security breach.

Make the smallest change that gets you through (site-specific tracking protection off, or a targeted site-data clear), then turn protections back up if you loosened them globally.