What Is ERR_PROXY_CONNECTION_FAILED? – Causes and Fixes
Learn what ERR_PROXY_CONNECTION_FAILED means, why the client never reached the proxy, and how to check settings, reachability, and credentials.
This error means the client could not connect to the configured proxy at all. The destination is irrelevant — the request never got past the first hop.
1. What the Error Means
The proxy itself is unreachable or not accepting connections.
- The site is not the problem. Nothing was ever sent toward it.
- A proxy is configured. On a machine that should not use one, that is itself the fault.
- It is a connection failure, distinct from an authentication refusal.
2. Common Causes
| Cause | Detail |
|---|---|
| Stale configuration | A proxy left behind by a removed VPN, extension, or corporate profile |
| Wrong host or port | Typos, or a port that changed |
| Proxy service down | The endpoint exists but is not running |
| Network cannot reach it | Firewall blocking the proxy's port, or it is only reachable internally |
| Automatic configuration script unreachable | A PAC file URL that no longer resolves |
| Extension interference | A browser extension setting a proxy the user did not choose |
On personal machines the leading cause is a proxy configured by software that is no longer installed.
3. Diagnosing It
First, determine whether a proxy should be in use at all — check the system network settings and the browser's own proxy configuration, including extensions that can override it.
Then test reachability of the proxy endpoint directly:
curl -sv --connect-timeout 5 -x "http://proxy.example.net:8000" http://example.com/ 2>&1 | head -15
A connection refusal or timeout here confirms the proxy is unreachable rather than misconfigured in some subtler way.
4. Fixing It
- Remove the proxy setting if none should be used. This resolves most personal-machine cases.
- Correct host and port against current documentation.
- Confirm the service is running and listening on the expected interface.
- Check firewall rules allowing outbound access to that port.
- Disable proxy-setting extensions and re-test.
- Verify PAC file reachability where automatic configuration is in use.
5. Versus Related Errors
ERR_TUNNEL_CONNECTION_FAILED— the proxy was reached, and the HTTPS tunnel failed.407— the proxy was reached and demanded credentials.ERR_CONNECTION_REFUSED— no proxy involved; the destination refused.ERR_NAME_NOT_RESOLVED— the proxy's own hostname could not be resolved.
The ordering is diagnostic: this error is the earliest possible failure in a proxied request.
6. In Automated Collection
For a client using a proxy pool, this failure identifies a dead endpoint rather than a blocked target. Remove it from rotation temporarily, record the failure per endpoint, and re-test after a cool-down.
If every endpoint fails simultaneously, the problem is credentials, network egress, or the provider — not the pool.
7. Real-World Examples
- A laptop that keeps a corporate proxy setting after leaving the network.
- A browser extension quietly configuring a proxy that later shuts down.
- A container whose environment sets a proxy variable pointing at a host outside its network.
- A provider endpoint retired while still present in a hard-coded list.
8. Summary
ERR_PROXY_CONNECTION_FAILED means the client never reached its configured proxy, so the destination was never contacted.
Check first whether a proxy should be configured at all, then verify host, port, service health, and firewall path. In pooled collection, treat it as a dead endpoint rather than as a blocked target.