@axlaim
All of the following, is a response by ChatGPT:
ERR_TUNNEL_CONNECTION_FAILED usually points to a problem in the browser’s network path rather than the website itself. The word “tunnel” is the clue: it often involves a proxy, VPN, filtering software, DNS-over-HTTPS, antivirus web filtering, or another component sitting between the browser and the destination.
Since:
- Firefox works normally.
- Brave fails only ~30% of the time.
- Sometimes the page loads after a delay.
I’d focus on something Brave is doing differently from Firefox.
Possible causes, roughly in order of likelihood:
1. Brave’s Secure DNS (DoH)
Brave may be using a different DNS path than Firefox.
Ask the user to test:
Settings → Privacy and Security → Security → Use Secure DNS
- Turn it off temporarily and test.
- If already on “Automatic”, try selecting a specific provider.
- If using a custom provider, switch back to Automatic.
Intermittent DNS failures can manifest exactly this way.
2. VPN or Proxy Configuration
ERR_TUNNEL_CONNECTION_FAILED is a classic proxy-related Chromium error.
Check:
Settings → System → Open your computer's proxy settings
and Windows:
Settings → Network & Internet → Proxy
Look for:
- Corporate proxy
- Old proxy entries
- Auto-detect settings that occasionally fail
- VPN client software
Even if the user doesn’t think they’re using a proxy, security products sometimes install one locally.
3. Antivirus / Security Suite HTTPS Inspection
Products such as:
- Norton
- Bitdefender
- Kaspersky
- ESET
- McAfee
often intercept HTTPS traffic through a local proxy.
A flaky HTTPS inspection component can produce intermittent tunnel failures in Chromium-based browsers while Firefox remains unaffected.
Temporarily disabling web protection (not necessarily the whole AV) is a useful test.
4. Brave Extensions
An extension that filters traffic can create this symptom:
- Ad blockers (in addition to Brave Shields)
- VPN extensions
- Privacy extensions
- Security extensions
Test in a fresh private window with extensions disabled, or create a new Brave profile.
5. Corrupted Network State in Brave
Chromium browsers occasionally develop network stack issues.
Things to try:
brave://net-internals/#dns
brave://net-internals/#sockets
Then restart Brave.
6. IPv6 Problems
Some ISPs or routers have unstable IPv6 connectivity.
Symptoms often include:
- Random failures
- Eventual success after retry
- Browser-specific behavior
Testing with IPv6 disabled temporarily can help isolate this.
7. Compare Brave and Firefox DNS Settings
Firefox can use its own DNS resolver independent of the OS.
If Firefox is using its built-in DNS-over-HTTPS and Brave is using Windows DNS (or vice versa), that difference alone can explain why only Brave is affected.