Not being able to reach a website and a website being down are two very different situations. They look identical from inside your browser — a blank page, a timeout, an error — but they have completely different causes and different solutions. Getting the diagnosis right in the first 30 seconds saves a lot of wasted troubleshooting.
The four reasons a site appears unreachable
1. The site is actually down — their servers are failing, overloaded, or unreachable from anywhere in the world. This is the only case where nothing you do locally will help.
2. The site is blocked in your country or region — governments, ISPs, and network administrators sometimes block specific domains. The site is working for everyone else.
3. The site is blocked on your network — corporate firewalls, school networks, and parental controls can block specific URLs without blocking your internet access otherwise.
4. You have a local DNS or routing issue — your device or ISP's DNS server cannot resolve the domain, even though the site is perfectly accessible from everywhere else.
How to diagnose in 60 seconds
Start with a server-side check at WebsiteDown.com. This checks the site from external infrastructure. If the probe succeeds, the site is up globally — your problem is local. If the probe fails, the site has a real outage.
If the site is up globally but you cannot reach it, try the following in order: open a new incognito window (rules out browser cache). Switch from Wi-Fi to mobile data or vice versa (rules out your specific network). Try on a different device (rules out device-specific issues). Try a VPN with a server in a different country (rules out regional blocks or ISP filtering).
If the site works on mobile data but not your Wi-Fi, the issue is your local network or router. If it works via VPN but not without, you are likely dealing with a regional block or ISP-level filtering.
The DNS test
A surprising number of "site is down" reports are actually DNS failures. Your device cannot translate the domain name into an IP address, so it never even tries to connect.
Flushing your DNS cache often fixes this immediately. On Windows, run 'ipconfig /flushdns' in Command Prompt. On macOS, run 'sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder' in Terminal. On iOS and Android, toggling Airplane Mode on and off clears the local DNS cache.
Switching your DNS resolver to 1.1.1.1 (Cloudflare) or 8.8.8.8 (Google) can also bypass an ISP's DNS server if that is the source of the problem. Both can be set at the network adapter level in your operating system settings.
Reading the error message
Your browser's error messages contain useful diagnostic information if you know what to look for.
"ERR_NAME_NOT_RESOLVED" or "DNS_PROBE_FINISHED_NXDOMAIN" means DNS failed — the domain could not be looked up. Start with a DNS flush or resolver change.
"ERR_CONNECTION_REFUSED" means DNS worked (the domain resolved) but the server actively rejected the connection. The site is probably down or the port is blocked.
"ERR_CONNECTION_TIMED_OUT" means your request reached a router or firewall that dropped it silently. Could be a network block, a regional restriction, or an overloaded server.
"ERR_CERT_INVALID" or "ERR_SSL_PROTOCOL_ERROR" means the connection reached a server but the SSL certificate failed — often a misconfigured server or, rarely, a MITM interception on your network.
Matching the error to the cause lets you skip the guesswork and go straight to the right fix.