NobleProxy

Proxy tunnel errors

Fix ERR_TUNNEL_CONNECTION_FAILED

Chrome shows ERR_TUNNEL_CONNECTION_FAILED when the CONNECT tunnel through your proxy cannot be established or is refused before the target site answers.

Quick answer

ERR_TUNNEL_CONNECTION_FAILED means the proxy refused or dropped the CONNECT tunnel. Fix the proxy address or credentials, then reload the page.

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Exact error text
Likely causes ranked
Ordered diagnostics
Verified remedy

When this is the right fit

  • Exact error text
  • Likely causes ranked
  • Ordered diagnostics

Who this page is for

Chrome shows ERR_TUNNEL_CONNECTION_FAILED when the CONNECT tunnel through your proxy cannot be established or is refused before the target site answers.

ERR_TUNNEL_CONNECTION_FAILED means the proxy refused or dropped the CONNECT tunnel. Fix the proxy address or credentials, then reload the page.

Diagnosis tree

ERR_TUNNEL_CONNECTION_FAILED on every site, immediately

Likely causes

  • - Proxy host or port is wrong, so nothing is listening
  • - The endpoint is paused or expired
  • - A local firewall blocks the endpoint port

Verified remedy

Re-copy host and port from the dashboard exactly, confirm the endpoint is active in your NobleProxy dashboard, then retry. A refused tunnel that survives correct values is almost always a local firewall rule.

ERR_TUNNEL_CONNECTION_FAILED only on HTTPS sites

Likely causes

  • - Client cannot authenticate to the proxy
  • - An interception tool (antivirus HTTPS scanning) fights the tunnel

Verified remedy

Confirm the username and password character-for-character (no trailing spaces), and temporarily disable HTTPS scanning to test. Reload the page after each change.

Error appears intermittently under load

Likely causes

  • - Too many connections for one endpoint
  • - Target or proxy dropped a keep-alive connection

Verified remedy

Lower concurrent tabs or connections through this endpoint to one or two, retest, then scale up gradually. Persistent endpoints are shared by nothing else - load is from your own clients.

Final connection check

  1. 1Fix the suspected cause
  2. 2Fully close and reopen the browser
  3. 3Reload the page that failed
  4. 4Load an IP echo page to confirm the exit address

Working connection

The page loads and the IP echo shows your assigned endpoint address.

Broken connection

The same error after correct values means the endpoint is unreachable: test the endpoint with curl -x before blaming the browser.

Sources

Facts last reviewed 2026-09-01.

Prevent it recurring

Save the working endpoint values in your profile notes and keep one endpoint mapped to one browser profile. Most repeat ERR_TUNNEL_CONNECTION_FAILED incidents start when two tools are pointed at different ends of the same mapping.

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Frequently asked questions

What does ERR_TUNNEL_CONNECTION_FAILED mean?

The browser asked your proxy to open a CONNECT tunnel to the site and the proxy refused or dropped it. The target site itself was never reached.

How do I fix ERR_TUNNEL_CONNECTION_FAILED in Chrome?

Re-check the proxy host, port, username, and password, make sure the endpoint is active, disable HTTPS-scanning antivirus temporarily, and reload. Then confirm the exit IP on an echo page.

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