Site Down Right Now

How to fix ERR_QUIC_PROTOCOL_ERROR

Updated 15 October 2026 · Site Down Right Now

Is the website down, or just you?

Chrome connects to many modern websites using QUIC, the protocol behind HTTP/3. It runs over UDP instead of the usual TCP. ERR_QUIC_PROTOCOL_ERROR means that QUIC connection broke and Chrome didn't fall back to a normal connection in time.

Common causes are a firewall, antivirus, VPN or work network that blocks or interferes with UDP traffic, a browser extension, or an out-of-date DNS answer that sends Chrome to a different server from the one it remembers supporting HTTP/3, for example just after a site moves host.

Check the site first

Enter the address in our website checker. If the site is up for us, the fault is in your browser or network.

Fixes that usually work

  1. Reload the page with Ctrl+Shift+R (Cmd+Shift+R on Mac). Chrome often falls back to a normal connection on the second try.
  2. Clear Chrome's host cache. Open chrome://net-internals/#dns, click Clear host cache, then go to chrome://net-internals/#sockets and click Flush socket pools.
  3. Flush your computer's DNS with ipconfig /flushdns (Windows) or restart your router if the site recently changed host.
  4. Turn off extensions, especially VPN, proxy and ad-blocking ones, or test in an Incognito window with extensions disabled.
  5. Pause your VPN or antivirus web protection, then try again. Some intercept HTTPS traffic in a way that breaks QUIC.
  6. Turn QUIC off as a last resort. Go to chrome://flags/#enable-quic, set Experimental QUIC protocol to Disabled and relaunch Chrome. Sites will still work over normal HTTPS, just without HTTP/3.

If you run the website

If many visitors see this error, check that UDP port 443 is open end to end and that your CDN or load balancer doesn't advertise HTTP/3 (the alt-svc header) on servers that can't serve it. If you've just moved hosts, visitors with stale DNS may still reach the old server, which can cause this error until their DNS cache refreshes.

Questions

Is it safe to disable QUIC in Chrome?

Yes. Websites fall back to standard HTTPS over TCP. You lose a little speed on some sites, nothing more. You can turn it back on at chrome://flags/#enable-quic.

Why do I only get ERR_QUIC_PROTOCOL_ERROR on one network?

That network, often a workplace, school or public Wi-Fi, probably blocks or limits UDP traffic, which QUIC needs. Try another network or disable QUIC.