Two gears where one is jammed, symbolizing browser mismatch
If a website loads fine in Chrome but fails in Firefox (or the other way around), it’s rarely “the internet is down.” It’s usually one browser-specific setting, a blocked cookie, an extension, or cached data that’s out of sync.

Let’s narrow it down quickly without breaking your logins.

Before you start: Note the exact symptom (blank page, infinite spinner, “secure connection failed,” missing buttons, upload not working). Different symptoms point to different fixes.

1. Confirm it’s really browser-specific (same network, same account)

Use the same Wi‑Fi/Ethernet connection and try the same URL in two browsers back-to-back.

  • If it fails in all browsers, focus on network/DNS/security software.
  • If it fails in only one, you’re hunting a browser setting, extension, cache, or profile issue.

Also try the site in a Private/Incognito window in the “bad” browser—this quickly rules out a lot.

2. Test in a clean session: Incognito (Chrome) vs Private Window (Firefox)

Mask and shield icons representing private browsing test
Private/Incognito mode disables most extensions and uses a fresh session, which is perfect for diagnosing “works here, not there.”

  • Chrome: Menu (⋮) → New Incognito window
  • Firefox: Menu (≡) → New Private Window

If the site works in a private window but not a normal one, it’s almost always one of these: extension interference, blocked cookies, corrupted site data, or a strict privacy setting.

3. Disable extensions (the fastest common cause)

Ad blockers, script blockers, privacy tools, password managers, and security extensions can behave differently across browsers—even with the same “brand” of extension.

  • Temporarily turn off all extensions in the browser that fails.
  • Reload the site.
  • If it works, re-enable extensions one at a time to find the conflict.

Pay extra attention to anything that blocks scripts/trackers, modifies headers, forces HTTPS, or changes DNS.

4. Clear site data for just that website (don’t nuke everything)

Cookie icon removed from a storage box
When one browser has stale cookies or cached files, the site can get stuck in a broken login loop, show missing UI, or fail to load certain resources.

  • Chrome: Settings → Privacy and security → Third-party cookies (or Site data) → See all site data and permissions → search the domain → Delete
  • Firefox: Settings → Privacy & Security → Cookies and Site Data → Manage Data… → search the domain → Remove Selected

Then fully close and reopen the browser (not just the tab) and try again.

5. Check cookie rules and tracking protection (Chrome vs Firefox differences)

Even if you “didn’t change anything,” browser updates can tighten defaults—especially around third-party cookies and tracking protection.

  • Firefox: Enhanced Tracking Protection set to Strict can break some sign-ins and embedded content. Try Standard temporarily for that test.
  • Chrome: Third-party cookie blocks (and “block all cookies”) can break login providers, payment pages, and CAPTCHA.

Practical test: allow cookies for that site (and any sign-in domain it uses), refresh, and try again. If it fixes the issue, you can add a site-specific exception instead of relaxing global privacy.

6. Compare DNS/HTTPS handling (secure connection errors and partial loading)

Chrome and Firefox can behave differently with DNS-over-HTTPS, cached DNS, and certificate validation—so a site might resolve or handshake in one browser but not the other.

  • Restart your router and your PC (this clears a lot of network state).
  • Temporarily disable VPN/proxy in Windows and in the browser.
  • If you use an antivirus “HTTPS scanning” feature, try pausing it briefly to test (then re-enable).

If the failing browser shows SSL/TLS errors (secure connection failed, invalid certificate, PR_END_OF_FILE_ERROR), the issue is often security software interception, a captive portal, or a network filter—not the website itself.

7. Try a fresh browser profile (when only one browser is “poisoned”)

If private mode still fails, your browser profile may be corrupted (settings, storage, service workers, extensions, or cached certificates).

  • Chrome: Create a new profile (Settings → You and Google → Add) and test the site there.
  • Firefox: Create a new profile (about:profiles in the address bar) and test.

If the site works in a new profile, you can migrate bookmarks/passwords carefully, or keep the new profile just for that service.

Final thoughts

When a site works in Chrome but not Firefox (or vice versa), treat it like a “differences audit”: extensions, site data, cookie rules, and network/security layers are the usual suspects.

If you tell support the exact browser + private-mode result + whether extensions were involved, you’ll skip most of the back-and-forth.