What Is the World Wide Web (WWW)?

The World Wide Web is an information system built on top of the Internet: a collection of documents and resources, pages, images, videos, applications, connected through hyperlinks and reachable with a browser. It is not a synonym for the Internet, even though everyday usage has long blurred the two.

It was invented by British scientist Tim Berners-Lee at CERN, the European particle physics laboratory near Geneva. In March 1989 he wrote the first proposal for a distributed information system that would let researchers at the lab share documents across different computers. By the end of 1990 he already had the first server and browser running, hosted on a NeXT machine at the address info.cern.ch.

On 30 April 1993, CERN placed the source code of the Web software into the public domain, free of charge and free of licence. That decision let anyone set up a server or build their own browser, and it drove adoption well beyond the scientific community.

Before the Web existed, the Internet already carried email and file transfers over FTP. Treating both terms as interchangeable is one of the most common mistakes: without the Internet there is no Web, but without the Web the Internet would keep running on other services.

The Web runs on four pieces that fit together. The HTTP protocol, and its encrypted version HTTPS, defines how a browser requests a resource from a server and how the server answers: the browser sends a request, the server processes it and returns a response with a status code, such as a 400 error when the request is malformed.

HTML is the language that structures the content of each page: headings, paragraphs, images, links, which the browser interprets to draw what shows up on screen. The URL is the unique address of each resource, made up of protocol, domain and path; sometimes it gets shortened with a URL shortener to make it easier to share in a message or an ad. And the hyperlink connects one document to the next, the element that gives the Web its network shape instead of a loose pile of separate files.

When someone types an address into a browser, it locates the right server, sends the HTTP request and gets the HTML back, translating it into the visible page along with the images and styles that page links to. At their core, these four elements have not changed since 1990: they still form the base of every page that loads today, even with layers of JavaScript, APIs and interactive applications stacked on top that make the process far richer than in its early years.

The term "World Wide Web" barely shows up in everyday speech anymore: people say "internet" when they mean the Web, and the WWW prefix has disappeared from most visible URLs. For anyone who works on websites, writes content for them or tries to get them ranking in a search engine, the technical distinction still matters.

Any technical SEO work starts from these same fundamentals: a server that answers with the correct HTTP codes, valid HTML and cleanly built URLs. Newer layers build on top of that base too, such as structured data, which lets search engines interpret a page as classified information rather than plain text.

Since 1994, the W3C (World Wide Web Consortium), founded by Berners-Lee himself, has maintained the standards that keep a page built in HTML looking the same across browsers, regardless of the vendor or the device it is opened on. Without that shared foundation, every site would need a separate build for every browser.

• Serve the whole site over HTTPS, not just HTTP, to encrypt the connection between browser and server.
• Use readable, stable URLs, without unnecessary parameters or frequent path changes.
• Validate HTML against W3C standards so different browsers do not interpret it inconsistently.
• Check internal and external hyperlinks regularly so they do not point to deleted pages.
• Configure HTTP status codes correctly, so a moved resource redirects instead of failing silently.
• Keep the server infrastructure up to date, since most availability failures start there, not in the browser.

• Treating "Internet" and "World Wide Web" as exact synonyms, when one is the network and the other a service running on it.
• Leaving broken links that return a 404 error instead of redirecting them to an equivalent page.
• Not monitoring server outages, which show up to visitors as a 500 error.
• Building URLs with uppercase letters, spaces or special characters that make them harder to read and index.
• Assuming a site "on the Web" is automatically accessible to everyone, without checking load times or browser compatibility.