Fix ERR_PROXY_CONNECTION_FAILED in Chrome

Short answers

These definitions and desktop settings labels were checked against Chromium’s current main-branch source on 4 October 2026. This is a documentation-checked diagnostic, not a recorded test in a specific Chrome release. Record your installed version from chrome://version; labels and configuration sources can differ.

Read the code before changing settings

A page saying only Unable to connect to the proxy server gives less evidence than the error code. Keep the code printed with it, the failed URL’s hostname and the time. Chromium’s network error definitions distinguish proxy connection, tunnel and mandatory-configuration failures.

Find the proxy Chrome is actually using

1. Open chrome://settings/system. When system settings supply the route, the control is labelled Open your computer's proxy settings.
2. If an extension supplies the settings, inspect that extension’s active proxy entry. Make sure you are checking the Chrome profile that failed.
3. If an administrator controls the route, inspect chrome://policy and send the proxy policy details to the administrator. Keep required rules in place.
4. If you launch Chrome from a shortcut, test runner or script, inspect any proxy launch options there. A system setting change may not alter that launch configuration.

On Windows 10 or 11, the system pane is Settings > Network & internet > Proxy. On macOS Tahoe 26, select the active network service in System Settings > Network, then Details > Proxies. Record whether the route uses a manual server, PAC URL or automatic discovery. The proxy settings guide explains those modes.

The Chromium settings source documents the system control and indicators for extension or administrator control. Its proxy documentation identifies policy, launch options, extensions and system settings as possible configuration sources.

Check the host and port together

1. Copy the gateway hostname again from the supplied connection details. Keep a URL scheme or credential URL out of a separate hostname field.
2. Compare the protocol and port as a pair. For Portproof’s authenticated HTTP route, use host gw.portproof.org and port 7000 from the connection builder.
3. If the proxy runs on your computer, confirm that its local process is running and listening on the configured port. An old local proxy entry can remain after the app stops.
4. If the server is on an organisation’s network, check whether the required network or VPN connection is available. Ask the administrator about permitted access to that host and port.

For an authenticated Portproof connection in Chrome, choose the HTTP endpoint. Chromium does not support SOCKS5 username/password authentication. An HTTPS destination can use an HTTP proxy through CONNECT; the destination scheme is not a reason to replace the gateway protocol or port.

Compare one explicit curl request

If you intentionally use Portproof, run this bounded check in an interactive POSIX terminal. Replace the username label with the complete generated username. curl asks for the proxy password; do not append it to the command. It makes one small request to the echo endpoint with certificate verification enabled.

curl_status=0
curl --disable --silent --show-error \
  --proxy 'http://gw.portproof.org:7000' \
  --proxy-user 'YOUR_FULL_PROXY_USERNAME' \
  --noproxy '' \
  --connect-timeout 5 --max-time 15 \
  --output /dev/null \
  --write-out 'connect_status=%{http_connect} target_status=%{response_code}\n' \
  'https://api.portproof.org/v1/echo-ip' || curl_status=$?
printf 'curl_exit=%s\n' "$curl_status"

This uses the diagnostic pattern in the existing curl guide; no new live-gateway or browser test is claimed here. --disable comes first to skip a default curl configuration file, and the explicit proxy with an empty exclusion list fixes the route for this check. Windows PowerShell needs curl.exe and adapted shell syntax. curl option reference.

A curl success confirms that curl reached the specified gateway for that request. It does not prove Chrome selected it. Conversely, curl against a manual host does not evaluate Chrome’s PAC script. For version-specific curl numbers and measured local examples, use the linked refusal and CONNECT guides.

When a required PAC configuration fails

For ERR_MANDATORY_PROXY_CONFIGURATION_FAILED, record the configured PAC URL and configuration source. Ask its owner to check availability, syntax and execution. Chrome’s PAC API can mark a script mandatory, preventing direct fallback when the script is invalid. Chrome PAC reference.

A script which cannot be obtained or evaluated is a different case from a valid script which selects an unreachable proxy. Use the exact error to retain that distinction. Do not clear a required script or add a direct fallback merely to suppress the message; that changes the intended route instead of repairing the configuration.

Keep a useful report

Record the UTC time, Chrome version, exact error code, configuration source, proxy host and port without credentials, destination hostname and the curl result if tested. If an authorised comparison from another network works, report that difference. Share passwords, API keys and credential URLs with neither a screenshot nor a public bug report.

If those details do not explain the route, Chromium’s NetLog instructions describe a capture with chrome://net-export. Use the default privacy mode, reproduce only the small failing request, then stop. Review the capture before sharing; sensitive URLs can still be present.

Sources and scope

Primary references checked on 4 October 2026: Chromium network errors, proxy behaviour, Chrome proxy API and curl documentation. Chromium main-branch definitions are not a verification of every installed Chrome release.

What is not allowed

Test only endpoints you are permitted to access and follow the acceptable-use policy.

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