Open chrome://flags/#enable-quic, set Experimental QUIC protocol to Disabled, and relaunch. Chrome then falls back to regular HTTPS over TCP. Also test without VPN and extensions, and allow UDP port 443 in your firewall.

What ERR_QUIC_PROTOCOL_ERROR actually means

QUIC is the protocol Google designed for faster connections. HTTP/3 runs over it. Chrome uses QUIC with Google services (YouTube, Gmail, Google Search) and many CDN-hosted sites. It runs over UDP port 443 instead of TCP.

Corporate firewalls, some antivirus suites, VPNs and older routers handle UDP poorly or block it. Chrome normally falls back to TCP automatically, but when packets are altered rather than dropped, you get ERR_QUIC_PROTOCOL_ERROR instead.

What you'll see

  • “This site can’t be reached. ERR_QUIC_PROTOCOL_ERROR”, often on YouTube or Google pages.
  • Videos stop loading or pages partly load.
  • Works in Firefox or on another network.

What causes ERR_QUIC_PROTOCOL_ERROR

  • Firewall, antivirus or VPN interfering with UDP 443 traffic.
  • A browser extension (proxy, VPN, ad-block) altering connections.
  • An outdated Chrome build with a QUIC bug.
  • Network equipment with buggy UDP handling.

How to fix it

  1. Disable QUICGo to chrome://flags/#enable-quic, choose Disabled and click Relaunch.
  2. Turn off VPN and extensionsDisconnect VPNs and test in Incognito. Disable proxy and VPN extensions.
  3. Check the firewallIn third-party firewalls or network gear, allow outbound UDP port 443, or block it completely so Chrome falls back cleanly.
  4. Update ChromeInstall updates at chrome://settings/help.
  5. Reset Chrome settingsIf nothing else works, use Settings → Reset settings → Restore settings to their original defaults.
How to confirm the fix: The affected Google or CDN pages load fully after relaunching Chrome.

Stop it happening again

Keep Chrome updated and avoid firewall rules that partially filter UDP traffic.