What happens in the second after you open a website

The short version

Opening a web page feels instant, but a small chain of events runs behind it. In plain terms, your device has to find the website, connect to it safely, ask for the page, and then build what it receives into something you can read.

Let us follow a single visit, step by step.

Step 1: Finding the address

Computers on the internet find each other using numbers called IP addresses (see What's an IP address?). People prefer names like example.com. So the first job is to turn the name into a number.

This is done by the Domain Name System, or DNS. It works like the contacts list on your phone: you tap a name, and the phone looks up the number. Your device asks a DNS service, usually run by your internet provider, "what is the number for this name?" and gets an answer back.

Answers are remembered for a while, so the next visit skips this step. That memory is called a cache.

Step 2: Connecting securely

Now your device contacts the website's server, the computer that holds the site (see What is a server?). The two agree how to talk and check that messages arrive complete.

For any address starting https, they also set up encryption: scrambling everything so that only your device and the server can read it. The server shows a digital certificate, a bit like an ID card, to prove it really is the site it claims to be. Your browser checks it. If all is well, you see the padlock or a similar icon beside the address.

Tip: The padlock means your connection is private, not that the site is honest. Scam sites can have a padlock too. Always check the web address itself is spelled correctly.

Step 3: Asking for the page

Your browser sends a short request, something like "please send me the home page". The server replies with the page's main file, written in a language called HTML that describes headings, paragraphs and links.

That file usually mentions many other pieces: pictures, fonts, styling files that control colours and layout, and small programs that make buttons and menus work. Your browser spots each of these and asks for them too, often dozens of requests for a single page. Some of them come from other companies, such as video players, maps or adverts.

Large sites often store copies of these pieces in many places around the world, so they can be sent from a server near you. This is one reason popular sites load quickly.

Step 4: Building the page

As the pieces arrive, the browser assembles them like a jigsaw. It lays out the text, applies the colours and fonts, places the images and runs the small programs. That is why you sometimes see text appear first and pictures fill in a moment later.

The browser also stores some pieces, such as the logo, so it does not need to fetch them again next time. And the site may leave a cookie to remember you. See Browsers and cookies.

When it goes wrong: what the messages mean

Want the technical version? See DNS explained and TCP, UDP and ports. You can also take apart a web address with the URL tool.