# Firefox: Hmm. We’re having trouble finding that site. / Server not found (DNS_PROBE or NS_ERROR_UNKNOWN_HOST)

**Code:** `Server not found` · **Category:** Browser · **Seen on:** Firefox, Windows, macOS

Firefox could not resolve the website’s hostname to an IP address — a typo, a DNS problem or no internet.

## Meaning

This is Firefox's version of DNS_PROBE_FINISHED_NXDOMAIN. Check the address, then whether other sites load. If only one site fails, its DNS records may be missing; if all fail, check connectivity, DNS servers and "DNS over HTTPS" settings.

## Common causes

- Typo in the address or a non-existent domain
- No internet connection
- Broken DNS server from the ISP/router
- DNS over HTTPS (Firefox default in some regions) blocked by the network
- VPN/proxy overriding DNS

## Quick fix

1. Check spelling and try again
2. Test another site and another network
3. Try different DNS (1.1.1.1) or turn off DNS over HTTPS in Settings

## Detailed fix by platform

### Firefox

1. Settings → General → Network Settings → Settings… → untick "Enable DNS over HTTPS" for a test
2. `about:networking#dns` shows resolver activity

### Windows

1. `ipconfig /flushdns`, then set DNS to 1.1.1.1 and 8.8.8.8

## How to diagnose

1. **Scope** — One site or all sites?
2. **DNS** — Does nslookup resolve?
3. **DoH** — Secure DNS blocked by network?

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Source: [WhatIsMyError](https://whatismyerror.com/errors/browser/firefox-server-not-found)