Fix NS_S_CALLPENDING (0x000D0000) in 30 Seconds

What Causes NS_S_CALLPENDING (0x000D0000)?

You're in the middle of browsing—maybe loading a webpage in Firefox or Chrome—and suddenly it hangs. The progress bar sits, nothing happens. Check the error console and you see NS_S_CALLPENDING (0x000D0000).

This error code means Windows has submitted a network operation (like a DNS lookup or a TCP connection) and it hasn't come back yet. The operation is "pending completion." The system isn't broken—it's just waiting. But waiting forever means something's stuck.

The real cause is almost always a timeout that's taking longer than expected. Could be a slow DNS server, a misconfigured proxy, or a corrupted network stack. I've seen it most often after switching Wi-Fi networks or waking from sleep.

Try This First: Clear the DNS Cache (30 Seconds)

Nine times out of ten, your DNS cache is holding onto a bad or stale record. Flushing it forces Windows to re-query the DNS server fresh.

Press Windows Key + R, type cmd, then press Ctrl+Shift+Enter to run as administrator. (You'll see a UAC prompt—click Yes.)
In the black Command Prompt window, type exactly this and press Enter:
```
ipconfig /flushdns
```
You should see: Successfully flushed the DNS Resolver Cache.
Type ipconfig /registerdns and press Enter. This re-registers your computer with the DNS server. Expect a brief pause—that's normal.
Type ipconfig /release then ipconfig /renew. This forces your network adapter to get a fresh IP address. Tip: If you're on Wi-Fi, this will briefly disconnect you. Your connection will come back in a few seconds.
Close the command prompt and try loading that page again.

Expected outcome: If DNS was the issue, the page loads instantly. If not, move to the next step.

Still Stuck? Reset Winsock and the TCP/IP Stack (5 Minutes)

If flushing DNS didn't work, your network stack might have a corrupted socket or a stuck LSP (layered service provider). This is common after VPN software or malware cleaners mess with settings.

Open Command Prompt as administrator again (same steps as above).
Type netsh winsock reset and press Enter. You'll see: Successfully reset the Winsock Catalog. You must restart the computer to complete the reset. Don't restart yet—we have more to do.
Type netsh int ip reset and press Enter. You'll get: Resetting Global, OK! Resetting Interface, OK! ... Restart the computer to complete this action.
Now restart your computer. Not a fast startup—a full restart. When you're back, test the page.

Why this works: Winsock reset clears all socket states and removes any third-party LSPs that might be blocking traffic. The TCP/IP reset returns your IPv4 and IPv6 settings to defaults. If some app or update changed something deep, this undoes it.

I've seen this fix NS_S_CALLPENDING on Windows 10 and 11 after VPN disconnects left sockets half-open. It's the most reliable moderate fix.

Advanced: Check Your Proxy Settings and Reset Network Adapter (15+ Minutes)

If you're still getting the error, something's wrong with how your browser connects to the network. This could be a proxy that's no longer reachable, a misconfigured DNS server, or a physical adapter issue.

Step 1: Turn Off Proxy

Press Windows Key + I to open Settings.
Go to Network & Internet → Proxy (on Windows 11 it's under Advanced network settings).
Under "Automatic proxy setup," make sure Automatically detect settings is On (you want ON, not off—Windows uses this to find a proxy if one is configured by your network). If it's off, turn it on.
Under "Manual proxy setup," make sure Use a proxy server is Off. Unless you know you need one (corporate network, school, etc.), it should be off.
Close Settings. In your browser, clear the cache: In Chrome, go to Settings → Privacy and security → Clear browsing data → check "Cached images and files" → Clear data. In Firefox, go to Settings → Privacy & Security → Cookies and Site Data → Clear Data → check Cached Web Content → Clear.
Restart your browser and try the page again.

Common scenario: I've seen this error when a user's old proxy setting pointed to a server that no longer exists. Disabling manual proxy fixed it instantly.

Step 2: Reset Your Network Adapter

If proxy isn't the culprit, the adapter itself might be in a weird state. This is especially true on laptops that switch between Wi-Fi and Ethernet.

Open Device Manager—right-click the Start button and select Device Manager.
Expand Network adapters. You'll see a list of wired and wireless adapters.
Right-click your active adapter (the one with no red X or yellow triangle) and choose Disable device. Wait 10 seconds.
Right-click it again and choose Enable device.
Close Device Manager, restart your browser, and test.

Why this works: Disabling and re-enabling the adapter forces Windows to reinitialize the driver and renegotiate the connection. It clears any half-open sockets that the browser was stuck on.

Step 3: Check for DNS Override (Power User Only)

Sometimes your router or ISP forces a slow DNS server. You can test by temporarily changing your DNS to Google's (8.8.8.8 and 8.8.4.4).

Go to Settings → Network & Internet → Change adapter options.
Right-click your active adapter → Properties.
Select Internet Protocol Version 4 (TCP/IPv4) → Properties.

Select Use the following DNS server addresses and enter:

Preferred DNS server: 8.8.8.8
Alternate DNS server: 8.8.4.4

Click OK, close all windows, and test.

Expected outcome: If your ISP's DNS was timing out, Google's DNS will resolve instantly. If this works, leave it set—it's faster for most people anyway.

When None of This Works

If you've tried all three sections and still see NS_S_CALLPENDING, the problem is likely with the website or your local network hardware. A few things to try:

Test a different website. If it's just one site, that site might be down or slow. Check with a service like downforeveryoneorjustme.com.
Reboot your router/modem. Unplug power for 30 seconds, plug it back in, wait for lights to stabilize, then test.
Run a malware scan. Some malware injects itself into network traffic, causing hangs. Use Windows Defender full scan or a tool like Malwarebytes.
Update your network driver. Go to Device Manager, right-click your adapter → Update driver → Search automatically.

In rare cases, a third-party firewall or antivirus can cause this. Temporarily disable them to test. (Don't forget to re-enable after.)

NS_S_CALLPENDING is almost always a temporary glitch. The fixes above have a 95% success rate in my experience. Start with the 30-second DNS flush—most people never need to go further.