What happens when you open a website, step by step

You type an address, press enter, and a page appears a moment later. In that moment your device and several other computers have a short, very fast conversation. Knowing the steps makes error messages much easier to understand, because each one points at a different step.

Step 1: finding the address (DNS)

Computers do not use names like example.com. They use numeric addresses, such as 203.0.113.10. The first job is to translate the name into a number, and that is what the Domain Name System, or DNS, does. Your device asks a DNS resolver, usually run by your internet provider or a public service, and the resolver either answers from memory or asks other servers until it finds the answer.

If this step fails you see messages such as DNS_PROBE_FINISHED_NXDOMAIN or “server not found”. The website itself may be perfectly healthy. Our guide to DNS and why it fails covers this step in detail.

Step 2: opening a connection

With the address in hand, your device contacts the server and they agree how to talk. This is called a TCP connection. It needs a small exchange of messages in both directions, so the time it takes depends on distance. A server on the other side of the world will take longer to answer than one in the same city, simply because signals take time to travel.

If this step fails you usually see “connection timed out” or “connection refused”. A timeout means nothing answered. Refused means a machine answered and said no, which usually means the software that should be listening is not running. See what a connection timeout means.

Step 3: making it private (TLS)

Almost every site now uses HTTPS. Before any page content is sent, your browser and the server agree on encryption keys, and the server shows a certificate that proves it really is the site you asked for. The browser checks that the certificate matches the name, has not expired and was issued by an authority it trusts.

When this fails you get a full-page warning about your connection not being private. The cause is nearly always the certificate: it has expired, it is for a different name, or your device clock is wrong. Read more in SSL certificate errors explained, or test any site with our SSL certificate checker.

Step 4: asking for the page (HTTP)

Now your browser sends the actual request: “please give me this page”. The server answers with a status code and, usually, the page. The status code is the three-digit number that tells you how it went. 200 means success. 404 means nothing lives at that address. The 5xx family means the server had a problem. Our status code guide explains each family.

For a large site this step is rarely handled by one machine. The request may go through a content delivery network, a load balancer, a web server and a database before an answer comes back. A fault in any layer can produce a 5xx error even though the front door is open.

Step 5: building the page

The first response is usually just the outline of a page. Your browser reads it and discovers it also needs style sheets, scripts, fonts and images, often from several different servers. It requests those too, in parallel, and then draws the page. A page can therefore “load” but look broken if one of those extra resources fails, for example when a font or script host is having its own outage.

Where each step can go wrong

• Name not found. DNS problem. Often fixed by flushing your DNS cache or trying another resolver.
• Timed out. The server is unreachable, overloaded, or something between you and it is dropping traffic.
• Certificate warning. The encryption step failed. Do not click through on a site that handles passwords or payments.
• 5xx error. The server was reached but could not do its job.
• Blank or half-drawn page. A supporting file failed, or something in your browser blocked it.

Why this matters when checking a site

When you use siteupdown.com we repeat these steps ourselves, from our server and from probes in other countries. Each run reports which step failed, not just whether the page opened, so you can tell “the site is down” from “the name does not resolve” from “the certificate has expired”. If every location can complete every step and you still cannot, the problem is almost certainly on your side. Our website not loading checklist walks through it.

A note on speed

Every step adds a little time, and a few of them depend on distance. This is why a site feels instant on a second visit: your browser and your DNS resolver remember answers, so steps 1 to 3 can be skipped or shortened. It is also why large sites place copies of their content in many cities, which is the idea behind a content delivery network.

Related guides

• What is DNS, and why does it fail?
• Website not loading? A step-by-step checklist
• How siteupdown.com checks a website, and what the verdicts mean

Last updated 2 November 2026. Written by the siteupdown.com team. Spotted a mistake?

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