What Is a URL? Structure and Components Explained

Every resource on the internet — every page, image, file or API endpoint — has a unique address called a URL. Understanding the structure of a URL helps you navigate the web, troubleshoot issues and build better websites.

Anatomy of a URL

Let's break down a full URL:

https://www.example.com:443/articles/guide?lang=en&page=2#summary

• Protocol — https:// — Defines how data is transferred. https is encrypted, http is not.
• Subdomain — www — Optional. Most sites use www or none at all.
• Domain — example.com — The website's registered domain name.
• Port — :443 — Usually omitted. Default is 443 for HTTPS and 80 for HTTP.
• Path — /articles/guide — Identifies the specific page or resource on the server.
• Query string — ?lang=en&page=2 — Optional parameters passed to the server, starting with ?. Multiple parameters separated by &.
• Fragment — #summary — Jumps to a specific section on the page. Processed by the browser, not sent to the server.

URL vs URI vs URN

• URL (Uniform Resource Locator) — Specifies location: https://example.com/page
• URI (Uniform Resource Identifier) — Broader term that includes URLs
• URN (Uniform Resource Name) — Identifies by name without location: urn:isbn:0-486-27557-4

In everyday use, URL and URI are used interchangeably.

Best Practices for URL Structure

• Use lowercase letters only
• Use hyphens (-) to separate words, not underscores (_)
• Keep URLs short and descriptive
• Include the target keyword in the path for SEO
• Avoid unnecessary parameters in URLs that should be indexed
• Use canonical URLs to handle duplicate content

Absolute vs Relative URLs

• Absolute URL — Full address including protocol and domain: https://example.com/about
• Relative URL — Path only, relative to the current page: /about or ../images/logo.png

Use absolute URLs in canonical tags, sitemaps and external links. Use relative URLs internally to make a site easier to move between environments.