The full form of WWW is:

Concept

An initialism spells a name out with the first letter of each of its words, so expanding it means recovering the exact words the coiners chose — not any phrase whose words merely begin with the same letters. WWW names the hypertext information system Tim Berners-Lee built at CERN: proposed in 1989, named World Wide Web in 1990, and opened to the wider public in 1991. Its documents are written in HTML, addressed by URLs and fetched over HTTP.

Applying it here

1. The opening W stands for World: the design goal was to reach documents held on computers anywhere on the Internet, not just inside one laboratory.

2. The middle W stands for Wide: together with World it states the system's extent, the same sense of "wide" carried by wide area network (WAN).

3. The closing W stands for Web: hyperlinks join the documents into an interconnected mesh — a web — instead of a single central catalogue.

Putting the three words together, WWW expands to World Wide Web.

Cross-check

• The naming carries through to the standards body: the organisation Berners-Lee founded in 1994 to maintain these standards is the World Wide Web Consortium (W3C), and the hostname prefix www. on a site address is the same abbreviation.

• "White" is a colour word, at home in coinages such as whitelist and white paper; it never entered the name of this system, so World White Web and Worst White Web are not expansions of WWW.

• "Worst" is the superlative of bad, a judgement of quality used in phrases such as worst-case complexity; a technical system is not named after a quality ranking, so Worst Wide Web and Worst White Web are not expansions of WWW.

Hence the full form of WWW is World Wide Web.