A URL (uniform resource locator) is the full address of a web page, including the protocol, domain and path.
A URL, or uniform resource locator, is the complete address of something on the web: a page, an image, a file or an API endpoint. When you type https://example.com/blog/my-post into a browser, that whole string is the URL. It tells the browser which protocol to use, which server to contact and exactly which resource to ask for.
People often use URL, web address and domain as if they mean the same thing. They don't. The domain, example.com, is just one part of the URL.
The parts of a URL
Take https://shop.example.com:443/products/shoes?colour=red#reviews:
- Scheme: https, the protocol. Most sites now use HTTPS.
- Host: shop.example.com, the domain example.com with shop as a subdomain and .com as the TLD.
- Port: 443, usually left out because browsers assume 443 for HTTPS and 80 for HTTP.
- Path: /products/shoes, the specific page or file on the server.
- Query string: ?colour=red, extra parameters, often used for filters, searches and tracking.
- Fragment: #reviews, a jump link to a section of the page. It isn't sent to the server.
How a URL is used to load a page
- The browser reads the scheme and host.
- It looks up the host in DNS to find the server's IP address.
- It connects to the server on the right port and, for HTTPS, checks the SSL certificate.
- It requests the path and query string.
- The server sends back the resource, an error such as 404 if it doesn't exist, or a redirect to a different URL.
URL vs domain vs URI
- Domain: the registered name, like example.com.
- URL: a full address that says how and where to fetch something.
- URI: the broader family of identifiers. Every URL is a URI, but not every URI is a URL.
URL best practice for SEO
Clean URLs help both visitors and search engines understand a page before they open it:
- Keep them short, readable and lowercase
- Use hyphens between words rather than underscores
- Avoid long strings of parameters where you can
- Pick one version of your site, with or without www and always on HTTPS, and redirect the others to it
- Don't change URLs without setting up 301 redirects, or you'll lose links and rankings
Common URL problems
Broken links after a redesign, pages reachable at both http and https, duplicate content at several URLs, and special characters that aren't encoded properly are the usual culprits. A redirect plan and a consistent URL structure solve most of them.