A Website Won't Open

When one site won’t open and others do, work along the chain your browser follows: the name, the connection, the certificate, the route.

1. Is it only this site?

If other sites don’t open either, run Internet Check first. See The internet is slow or keeps dropping.

2. Does the name resolve?

In DNS Lookup, look up the site’s A record.

• Domain does not exist (NXDOMAIN): a typo, or the domain has lapsed. Whois shows when it expires.
• No answer from your resolver, but an answer from Custom DNS such as Cloudflare: your provider’s or router’s DNS is the problem. Switch DNS servers in the router or in macOS.
• The site recently moved: check DNS Propagation. Your resolver may still have the old address.

3. Does the server answer?

In Path Check, check ports 443 and 80 on the site.

• Reachable: the server is up and listening.
• Refused: the machine is up, but no web server runs on it.
• Timed out: the server is down, or a firewall or VPN is in the way.

4. Is the certificate fine?

If the browser warns that the connection isn’t private, open SSL Certificate. It names the problem: expired, a name mismatch, or an incomplete chain, which explains a site that works in one browser and fails elsewhere.

5. Where does the route break?

If the server doesn’t answer, Traceroute shows how far your traffic gets. When the trace dies inside your provider’s network, the problem is between you. When it reaches the site’s network, it’s theirs.

Tip: If the site works on your phone over mobile data but not on your Wi-Fi, it’s your network or your provider: DNS, a filter on the router, or a block. If it fails everywhere, the site itself is down.

Related

• DNS, Ports and Certificates.