The essential points from this guide -- each one is explained in detail below.
TL;DR: Checking the proxy and the firewall means testing proxy settings, firewall rules, and DNS one at a time, since a single browser error message covers all three possible causes at once.
Chrome's "check your proxy, firewall, and DNS configuration" message appears for several different connection failures, not one specific cause.
Wrong or leftover proxy settings on Windows or Mac block connections the same way a firewall rule does, so check both.
A firewall blocking a specific port or app produces the same error message as a broken proxy configuration.
Flushing DNS and testing with the proxy temporarily disabled isolates whether DNS, the proxy, or the firewall is the actual cause.
Browsers show a proxy and firewall warning when a page request never gets a response and the browser cannot tell why. Chrome's version of this message typically reads something like "check your proxy, firewall, and DNS configuration," and it shows up alongside error codes like ERR_CONNECTION_REFUSED, ERR_CONNECTION_TIMED_OUT, or ERR_NAME_NOT_RESOLVED. Windows shows a similar generic message when its own network troubleshooter cannot pin down the cause. For a quick definition of the first term in that message, see what a proxy is.
The reason the message lists three separate systems is that all three can produce the exact same symptom: a page that never loads. A misconfigured proxy sends your request nowhere useful. A firewall rule can block the connection before it leaves your device or router. A broken DNS setting means your device cannot find the right address to connect to in the first place. Checking the proxy and the firewall, and then DNS, one at a time is the only reliable way to tell which of the three is actually responsible, instead of guessing.
A web request from your browser passes through several layers before it reaches a website: your browser, your operating system's network settings, any proxy configured on the device, your firewall, your router, and finally the internet. A block or misconfiguration at any single layer stops the whole request, and the resulting error often looks identical no matter which layer caused it.
A proxy sits between your browser and the internet on purpose, forwarding requests through a different server. If that proxy address is wrong, offline, or requires authentication your browser is not sending, every request through it fails. A firewall works differently: instead of forwarding traffic, it inspects each connection against a set of rules and drops anything that does not match, whether that is a blocked port, a blocked app, or a blocked destination. A firewall is also not the same thing as a VPN or a proxy; see proxy vs VPN for how the three differ. Software firewalls, built into Windows and macOS, and network firewalls, built into routers or corporate networks, can both block the same connection independently, so checking the proxy and the firewall and dns configuration together, rather than assuming one is the cause, is worth doing before changing any setting.
How do I check the proxy and firewall starts with the proxy, since it is the setting most likely to have changed without you noticing.
On Windows: 1. Open Settings and go to Network & Internet, then select Proxy from the left menu. 2. Check whether "Automatically detect settings" or "Use setup script" is turned on when you did not turn it on yourself; some VPN apps and browser extensions enable this without asking. 3. If "Use a proxy server" is turned on and you do not recognize the address, turn it off and try loading the page again. 4. Restart the browser after any change, since some proxy settings only apply to new browser sessions.
On Mac: 1. Open System Settings, then Network, then select your active connection (WiFi or Ethernet) and click Details. 2. Click Proxies and check which protocols (Web Proxy, Secure Web Proxy, SOCKS Proxy) are checked on. 3. Uncheck any proxy you do not recognize, then click OK and try the page again.
On a managed work laptop, an IT department may push proxy settings you cannot change yourself; if these steps show a proxy you did not set, contact IT before removing it.
On Windows, open Settings, then Privacy & Security, then Windows Security, then Firewall & Network Protection. Check whether the active network profile is turned on, then click "Allow an app through firewall" to see if the specific app or browser you are using is blocked. On Mac, open System Settings, then Network, then Firewall, and check the list of allowed apps the same way.
DNS problems produce a failure that looks similar to a firewall block, since your device cannot resolve a domain name to an address at all. Flush the DNS cache to rule this out: on Windows, run ipconfig /flushdns in Command Prompt; on Mac, run sudo dscacheutil -flushcache in Terminal. If the page loads after flushing DNS, the proxy and firewall were never the problem. See how proxies work for the full request path DNS sits alongside.
How to check proxy and firewall on chromebook works differently, since Chrome OS manages both through one settings panel: open Settings, search "proxy," and review the network's proxy tab directly, since Chromebooks do not have a separate OS-level firewall panel the way Windows and Mac do.
The most common mistake is changing several settings at once, which fixes the connection but leaves you unsure which change actually worked. Change one setting, one layer, at a time, and test the page again after each change before moving to the next one.
A second common mistake is assuming a proxy problem is the firewall's fault, or the other way around, without testing either directly. Temporarily disabling the proxy, if one is set, isolates whether the proxy itself is the cause. Temporarily disabling a third-party firewall, never the device's only firewall, and only briefly, isolates whether a firewall rule is the cause.
A third mistake is skipping the browser restart after a settings change. Some proxy and DNS settings only take effect for new connections, so a page that still fails right after a fix may just need the browser, or the device, restarted before the change applies.
If you are using a proxy on purpose, for scraping, testing, or privacy, and this error shows up, the cause is often the proxy connection itself rather than Windows or Chrome's own settings. Work through these checks before touching your operating system's firewall:
1. Confirm the proxy hostname and port are typed correctly; a single typo produces the exact same connection-refused symptom as a real block. 2. Test the proxy directly with a command-line tool before blaming the browser. On Mac or Linux, run curl -x http://USERNAME:PASSWORD@host:port https://example.com; on Windows, use the same command in PowerShell if curl is installed, or a tool like Postman. 3. Check whether the proxy requires authentication your browser is not sending. Some proxies need a username and password in the connection string, not just the host and port. 4. Confirm your firewall is not blocking the proxy's specific port outbound, separate from blocking inbound connections, since outbound port blocks are less common but do happen on locked-down corporate networks.
If the curl test succeeds but the browser still fails, the problem is in how the browser or app is configured to use the proxy, not the proxy itself. If the curl test also fails, the proxy, your credentials, or the port is the actual cause, and no amount of firewall or DNS troubleshooting will fix it. If your own proxy turns out to be the cause and you need a more reliable one, compare residential proxies and current rates on the pricing page.
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KnoxProxy Research Team · Technical Content
Network engineers and proxy infrastructure specialists with 10+ years in anti-bot systems, web scraping, and IP routing.
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