Fix NS_E_PROXY_DNS_TIMEOUT 0XC00D2EF0 in 3 steps

The 30-second fix: Flush your DNS cache

Most of the time, NS_E_PROXY_DNS_TIMEOUT shows up because Windows is holding onto a stale DNS record for your proxy server. I’ve seen this happen when a company switches proxy providers but machines still try to resolve the old IP. Quickest way out is to dump that cache.

Open Command Prompt as Administrator. Hit Start, type cmd, right-click Command Prompt, and pick Run as administrator.
Type ipconfig /flushdns and press Enter. You’ll see Successfully flushed the DNS Resolver Cache.
Now test your connection. Open a browser and try to load a site. If it works, you’re done. If not, move to the next step.

I had a client last month whose entire office couldn’t reach their hosted ERP because of this. One ipconfig /flushdns on each machine and they were back in business. Takes 30 seconds.

Pro tip: If you’re on a corporate network, this might not be enough — your proxy might be auto-detected via WPAD. The flush clears the client side, but the proxy’s DNS record itself could be the problem. But try this first anyway.

The 5-minute fix: Check your proxy settings

If flushing didn’t help, Windows might be pointing to a dead or wrong proxy server. This error usually hits on Windows 10/11, but I’ve seen it on Windows 7 machines that never had their proxy settings updated after a migration.

Step 1: Verify proxy configuration

Press Win + R, type inetcpl.cpl, and hit Enter.
Go to the Connections tab and click LAN settings.
Uncheck Use a proxy server for your LAN unless you know you need one.
Also check Automatically detect settings — this should be on if your network uses WPAD. If it’s off and you don’t have a static proxy, turn it on.

Step 2: Test without the proxy

After unchecking the proxy box, try loading a site. If it works, your proxy server is unreachable, misconfigured, or the DNS for it has changed. You’ll need to get the correct proxy address from your IT team or ISP. If the error goes away but you need the proxy for work, keep reading — the advanced fix covers that.

Step 3: Reset Internet Explorer settings (yes, it matters)

Windows still uses IE’s proxy stack under the hood for many apps. So resetting it can help:

In inetcpl.cpl, go to the Advanced tab.
Click Reset under Reset Internet Explorer settings.
Check Delete personal settings only if you’re okay losing saved passwords (I rarely do this — it’s overkill). Then click Reset.

Not a single reboot needed. If you’re still stuck after this, something deeper is wrong.

The 15+ minute fix: Winsock reset and proxy auto-configuration

If you’ve done the above and the error still pops up, your network stack might be corrupted. I’ve seen this on machines that had VPN clients installed and uninstalled sloppily — the Winsock catalog gets borked. Also, your company’s proxy auto-config (PAC) file might be failing to load.

Step 1: Reset Winsock

Winsock is the API Windows uses for network communication. Resetting it wipes out any bad protocol entries:

Open Command Prompt as Administrator again.
Type netsh winsock reset and press Enter. You’ll see a message saying it reset the Winsock catalog.
Type netsh int ip reset and press Enter. This resets your TCP/IP stack.
Reboot your machine.

I had a client last month whose print queue died because of a corrupted Winsock — unrelated but same fix. Reboot fixed it after the reset.

Step 2: Check your PAC file (if you use one)

If your network uses a proxy auto-config file (like proxy.pac), the DNS timeout could mean Windows can’t fetch that file. Open your proxy settings again (inetcpl.cpl > Connections > LAN settings). If you have a Use automatic configuration script box checked, try this:

Open a browser and navigate to that PAC URL directly (e.g., http://proxy.company.com/proxy.pac).
If it doesn’t load, the URL is wrong, the server is down, or DNS can’t resolve it. Contact your network admin for the correct URL.
If it loads but the script is malformed, that’s a different problem — but a DNS timeout could mask it.

Step 3: Bypass proxy for local addresses

Sometimes the timeout happens because the proxy is being used for internal resources that don’t need it. In the LAN settings window, check Bypass proxy server for local addresses. Also add any local IP ranges (like 192.168.*) to the exception list under Advanced.

Setting	What to do
Proxy server	Uncheck if not needed. Re-check with correct address if required.
Automatically detect settings	Turn on unless you have a static proxy.
Use automatic config script	Only if your company provides a PAC URL — verify it works.
Bypass proxy for local addresses	Check this to avoid proxy for internal traffic.

Step 4: Last resort — disable IPv6

I don’t like doing this, but IPv6 misconfigurations can cause DNS timeouts with proxies. If you’re desperate:

Open Network & Internet settings > Change adapter options.
Right-click your active connection, select Properties.
Uncheck Internet Protocol Version 6 (TCP/IPv6).
Restart your network adapter or reboot.

This is a symptom mask, not a fix, but it gets you online while you sort out the real problem. I’ve only needed this once — on a Windows 10 machine that had a buggy VPN driver interfering with DNS.

Final thoughts

The NS_E_PROXY_DNS_TIMEOUT error is annoying but rarely serious. Start with the DNS flush (30 seconds), then check your proxy settings (5 minutes), and only go to Winsock reset if you have to. Most people stop at step one or two. If you’re still stuck, your proxy server itself might be down — and that’s a call to your ISP or network admin, not a fix you can do at your desk.