Fix Firefox PR_CONNECT_RESET_ERROR on specific sites

Quick answer for advanced users: Open about:config, toggle security.tls.enable_0rtt_data to false, and clear your DNS cache with ipconfig /flushdns. If that fails, disable your proxy or VPN.

You're hitting a site you visit often — maybe your bank, a company portal, or a forum — and Firefox shows Secure Connection Failed with PR_CONNECT_RESET_ERROR. Chrome loads the same site fine. This isn't a random glitch. It's Firefox tripping over something in the TLS handshake or a proxy conflict. The error means the server closed the connection before the handshake finished. Most commonly, it's TLS 1.3 early data (0-RTT) or a misconfigured proxy. Let's fix it.

Fix Steps

1. Disable TLS 1.3 early data (0-RTT)
   This is the #1 cause on Firefox 90 and later. Type about:config in the address bar, accept the warning, and search for security.tls.enable_0rtt_data. Double-click it to set it to false. Reload the site. If it works, you're done. If not, undo this later — but 8 times out of 10 this is it.
2. Clear your DNS cache and socket pools
   Firefox caches DNS and SSL session data. Sometimes those get stale. Go to about:networking#dns and click Clear DNS Cache. Then go to about:networking#sockets and click Flush Socket Pools. Reload the site.
3. Check your proxy settings
   Go to Settings > Network Settings (under General). If you have a proxy enabled but don't need one (common with corporate VPNs that don't clean up), switch to No proxy. If you're behind a corporate proxy, make sure it's set correctly — ask your IT team for the exact address and port.
4. Disable HTTP/3 or QUIC
   Some older servers don't handle HTTP/3 well. In about:config, search for network.http.http3.enabled and set it to false. Reload. If the site loads, HTTP/3 was the problem.
5. Turn off your antivirus HTTPS scanning
   Bitdefender, Norton, and McAfee all have "SSL scanning" features that intercept HTTPS traffic. Disable it temporarily and reload. If the site loads, add it to the antivirus exclusion list or turn off HTTPS scanning for good.

Alternative Fixes (if the above fails)

• Create a fresh Firefox profile. Close Firefox, press Win + R, type firefox -P, create a new profile, and test the site. If it works, your old profile has corrupted data. Migrate bookmarks and passwords manually — don't copy the whole profile folder.
• Disable all extensions. Run Firefox in Safe Mode (hold Shift while starting). If the site loads, extensions are the cause. Disable them one by one until you find the culprit. Ad blockers and privacy extensions like uBlock Origin and HTTPS Everywhere are common triggers.
• Reset Firefox completely. Go to about:support and click Refresh Firefox. This keeps your bookmarks and passwords but resets everything else. It's nuclear but effective.

Prevention Tip

Once you fix this, check your Firefox update status. Mozilla pushed a change to TLS 1.3 0-RTT in Firefox 90 that broke a lot of sites. Keep Firefox updated, but if you hit a site that doesn't support 0-RTT, you'll have to leave security.tls.enable_0rtt_data set to false permanently. That's fine — it's a performance feature, not a security one, and dropping it doesn't hurt most users.

Also, if you use a VPN that has a built-in ad blocker or HTTPS filter, try switching it off when you hit this error. VPNs like NordVPN and ExpressVPN have caused this exact error on corporate sites.

One more thing: if the site works in Chrome but not Firefox, don't waste time reinstalling Firefox. It's almost never a broken browser — it's a configuration clash. The steps above cover 95% of cases.