How does the website down checker work?

It sends a controlled public HTTP request from the Netest server, follows safe redirects and reports whether a response was received, along with status, timing and the final URL.

Does an HTTP 404 or 500 mean the website is down?

No. A 4xx or 5xx response proves that an HTTP server answered, although a page or application may be unavailable. The checker separates a responding error from a connection failure.

Why can the result differ from my browser?

The check runs from the Netest server. DNS views, CDN location, firewalls, rate limits, VPNs and local network paths can make a website appear different from another location.

Can this check private or intranet websites?

No. Private, loopback, local, multicast and reserved destinations are blocked. Use local monitoring or command-line checks for internal services.

Full-stack website diagnostic

Why is my website not reachable?

Trace a public website request from DNS to the application. Netest checks each critical layer and highlights exactly where the connection breaks.

8 checks, one result Public targets only Tested from Netest

One request, every layer

DNSResolved

TCP / TLSConnected

HTTP503 response

Likely problem: application

Enter a website to diagnose

Use a domain or complete HTTP/HTTPS URL. Netest safely follows redirects and checks the public endpoint.

Live server-side checks

Try an example:

No history saved

Private, local, loopback, multicast, and reserved destinations are blocked.

Your diagnostic report will appear here

Run a check to see DNS, network, TLS, HTTP, redirects, and security-header results in one report.

One check, every critical layer

A website can disappear for very different reasons. DNS may point nowhere, port 443 may be blocked, a certificate may be invalid, or a healthy network may lead to an application returning a 503. This diagnostic checks those dependencies in order, so you can start troubleshooting at the layer that actually failed.

DNS & network

Resolve public addresses, confirm authoritative nameservers, identify the network owner, and test TCP 443.

TLS & certificate

Inspect certificate health, remaining validity, issuer, chain, and the negotiated TLS connection.

HTTP & application

Read the final HTTP status, response time, redirect path, and coverage of core security headers.

What to do with the result

DNS failed

Confirm the domain registration, authoritative nameservers, DNSSEC status, and A or AAAA records. Recent changes may still be propagating.

TCP failed

Check port 443 on your firewall, load balancer, CDN origin, hosting service, and web server. A refused connection differs from a timeout.

TLS warned or failed

Review certificate expiry, hostname coverage, intermediate certificates, SNI configuration, and the protocols accepted by the server.

HTTP failed

The network path is working. Inspect application, reverse-proxy, upstream, database, capacity, and deployment logs for the returned status.

Website diagnostic FAQ

Does this prove a website is down globally?

No. It is a live observation from the Netest server. Regional CDNs, WAF rules, split DNS, VPNs, and local ISP paths can produce different results.

Is a 404 or 503 a network failure?

No. An HTTP error proves the request reached a web server. A 404 is usually a route or content issue; a 503 usually means the application or an upstream dependency is unavailable.

Can I test localhost or an intranet?

No. Private, local, loopback, multicast, and reserved destinations are blocked. Use local diagnostics for internal services.

Why are redirects marked as a warning?

Redirects are common and often intentional, but a long or unexpected chain adds latency and can reveal a hostname or protocol configuration issue.

Related diagnostic tools

DNS Lookup for individual A, AAAA, MX, TXT, NS, SOA, and CNAME records.
SSL Checker for a deeper certificate and chain report.
HTTP Header Checker for raw response headers, caching, redirects, and cookies.
Security Headers Checker for detailed browser security policy guidance.