A URL — Uniform Resource Locator — is the complete address used to access a resource on the web. Every URL contains several parts: the protocol (such as https), the domain name, an optional path to a specific page, and sometimes a query string with extra data. Understanding URL structure helps explain how browsers find web pages.

What does URL stand for, and what is it for?

URL stands for Uniform Resource Locator. It is a standardised way of writing the address of any resource accessible over the internet — including web pages, images, videos, files, and APIs.

When you type a URL into a browser or click a link, the browser reads each part of the URL and follows a sequence of steps: it identifies the correct server using the domain name, asks that server for the specific resource identified by the path, and uses the protocol to determine how to communicate. Without URLs, the web would have no consistent, human-readable addressing system.

What are the parts of a URL?

A full URL has the following structure:

scheme://host:port/path?query#fragment

For example:

https://www.aitutors.me:443/blog/gcse?topic=computing#section2
Part Example Meaning
Scheme (protocol) https The communication protocol to use
Host (domain name) www.aitutors.me The server's human-readable address
Port 443 The numbered "door" on the server (usually omitted — defaults to 80 for http, 443 for https)
Path /blog/gcse The specific page or file on the server
Query string ?topic=computing Extra data passed to the server
Fragment #section2 A specific part of the page (handled by the browser, not sent to the server)

What do the scheme and port mean?

The scheme (also called the protocol) tells the browser which communication rules to use:

  • http — HyperText Transfer Protocol: the original web protocol, sends data as plain text.
  • https — HTTP Secure: the same protocol but with TLS encryption, making the connection secure. You can tell a site uses HTTPS by the padlock icon in the browser address bar.
  • ftp — File Transfer Protocol: used for transferring files (less common now).
  • mailto — not a web address; opens the user's email client.

The port is a number (0–65535) that identifies a specific service on the server. Most web traffic uses ports 80 (HTTP) or 443 (HTTPS), which are so standard that browsers omit them — you rarely see a port number in everyday URLs.

What is a domain name?

The domain name is the human-readable address of the server — for example, bbc.co.uk or aitutors.me. A domain name has several parts, read right to left by importance:

  • Top-Level Domain (TLD): the rightmost part — .com, .co.uk, .org, .me. The TLD hints at the organisation type or country.
  • Second-Level Domain: the organisation's chosen name — bbc, aitutors, google.
  • Subdomain: optional prefix — www, mail, learn. Different subdomains can point to different servers.

When a browser receives a URL, it asks a DNS (Domain Name System) server to convert the domain name into the server's numeric IP address — because computers route data using IP addresses, not domain names.

What is a path?

The path is the part after the domain name, separated by forward slashes (/). It identifies the specific resource on the server:

  • / alone means the root (home page) of the site.
  • /blog/gcse means the gcse page inside a blog directory.
  • /images/logo.png points to a specific file.

On the server, the path might correspond to an actual file and folder structure, or the server might interpret it dynamically to generate a page.

What is a query string and what is URL encoding?

A query string begins with ? and contains key=value pairs separated by &. It sends extra information to the server without changing the path:

https://www.example.com/search?q=computing+gcse&sort=newest

Here, q=computing+gcse is the search term and sort=newest is a filter option. The server reads these values and uses them to build the response.

URL encoding converts characters that are not permitted in URLs into a safe format. A space becomes %20 (or + in query strings). Other special characters are replaced with % followed by their hexadecimal code — for example, £ becomes %C2%A3. Browsers handle encoding automatically when you type a URL, but you may see encoded characters in the address bar.

Frequently asked questions

What is the difference between a URL and a web address?

"Web address" and "URL" are used interchangeably in everyday speech. Technically, a URL is the full address including the scheme, host, path, and so on. A URI (Uniform Resource Identifier) is a broader concept that includes URLs as well as other identifier formats. In KS3 computing, treating URL and web address as synonyms is fine.

What is the difference between a URL and an IP address?

An IP address (such as 142.250.187.68) is the numeric address of a server on the internet. A URL uses a human-readable domain name (such as www.google.com) in place of the IP address. The DNS system translates the domain name into an IP address behind the scenes. URLs are designed for people; IP addresses are used by computers to route data.

Can a URL contain spaces?

Not directly. Spaces and many other characters are not allowed in URLs. If you paste a URL containing spaces into a browser, the browser URL-encodes them automatically (replacing each space with %20 or + in the query string). When writing URLs in code or HTML, you should always encode special characters manually or use a URL-encoding function.

Why do some URLs end with .html and others have no extension?

Older websites often had a direct mapping between URLs and files on the server's disc, so the URL ended in .html (HyperText Markup Language) — the file type of a web page. Modern websites generate pages dynamically — a database query or server-side script produces the HTML on demand — so the URL path can look like /products/12 with no file extension. The server decides how to interpret the path regardless of whether it looks like a file name.

Explore how URLs, DNS, and HTTP requests fit together with Professor Turing at aitutors.me.