If your Vercel‑hosted site will not load, and a generic browser error appears instead of a Vercel error page, this is often due to local network or DNS issues. This can also occur if the upstream ISP is blocking access to Vercel, or in some countries, due to government-level website filtering, censorship, or blocks.
This guide will help you troubleshoot and determine if the issue is caused by DNS issues on your device, your local network (e.g. firewall rules), or an ISP-level or upstream block.
Copy link to heading1. Open your site in a private / incognito browsing window
Browsers can cache more than just images and CSS — they can hold DNS prefetch results, as well as SSL certificates. A private window prevents this and also turns off extensions/VPN plug-ins that might be interfering with DNS or proxy traffic.
Chrome / Edge / Brave: Ctrl + Shift + N (Windows) or ⌘ + Shift + N (macOS)
Firefox: Ctrl + Shift + P (Windows) or ⌘ + Shift + P (macOS)
- Site now loads → clear the normal browser cache (Settings → Privacy → Clear browsing data).
- Site still fails → proceed to step 2.
Copy link to heading2. Try a different network connection
Changing networks is the quickest way to tell whether the block sits inside your local network or ISP. A mobile hotspot is perfect for this because it bypasses home/office firewalls and usually uses the mobile carrier’s DNS resolvers.
- Disconnect from any existing Wi‑Fi/Ethernet connections.
- Enable your mobile phone's hotspot and connect your device to it.
- Load your site again.
- Site still fails on hotspot → The issue travels with the workstation. Proceed to Step 3 to flush its DNS cache.
- Site loads on hotspot → Your device isn't at fault, and something between the router and the wider internet is. Re‑connect to the problem network and continue to step 4 to gather diagnostics.
Tip: If the hotspot test works, but you’re on corporate Wi‑Fi, you may need your organization's IT department to allowlist your Vercel site.
Copy link to heading3. Check DNS resolution, then flush your device cache
Operating systems cache DNS answers for performance, but your upstream DNS resolver can also hold on to stale records. First, inspect what your machine and resolver are seeing, then flush only your local cache.
Copy link to heading3.1 Query your device's default DNS resolver
macOS / Linux (Terminal)
dig +nocmd your-site.com any +multiline +nocookie
Windows (PowerShell / Command Prompt)
nslookup your-site.com
Tip: Note the SERVER line (which resolver was used), every IP address returned, and the TTL value.
Copy link to heading3.2 Query trusted public resolvers
Query Google Public DNS (8.8.8.8) directly. These resolvers refresh records frequently and are seldom filtered, so they serve as a "trusted" baseline:
dig @8.8.8.8 your-site.com
| Scenario | Interpretation | Next action |
| Public and default match and look correct | Problem is likely isolated to your local device | Proceed to 3.3 Flush local cache |
| Public answers are correct, but default returns no record or wrong IP | Your ISP or upstream resolver is caching or blocking the request | Temporarily change your system DNS to 8.8.8.8. If your site now works, proceed to 4. Run the Vercel network debug script on the affected network |
| All resolvers return the wrong IP or NXDOMAIN | The authoritative zone may be misconfigured or the record may not yet be fully propagated | Wait for DNS propagation (up to 24) or reach out to your domain provider |
Copy link to heading3.3 Flush your device's local DNS cache
macOS / Linux (Terminal)
sudo dscacheutil -flushcache
sudo killall -HUP mDNSResponder
Windows (Command Prompt)
ipconfig /flushdns
Copy link to heading3.4 Compare the result
Run the same queries one more time.
- TTL resets and/or IPs change and your site now loads → Your local device was holding a stale DNS entry.
- Lookup answer unchanged or still incorrect → The resolver or ISP cache is stale; continue with step 4 while connected to the problematic network.
Copy link to heading4. Run the Vercel network debug script on the affected network
This script will conduct various checks, and depending on different factors, it may take up to 15 minutes to finish. When complete, it will create a vercel-debug.txt file in the current working directory, which you then can attach to your open support case with Vercel Support.
Access the Vercel network debug script here: https://github.com/vercel-support/vercel-connect-debug?tab=readme-ov-file#commands-to-run
Copy link to heading5. Send results to Vercel Support
For Contact Vercel Support or raise an issue in the Vercel Community, and include the following:
- Attach the
vercel-debug.txtfile to your support case or post - The site URL
- The approximate time the issue occurred (with your local timezone)
- Confirmation you have followed the steps above