One of the original developers of WWW along with Tim Berners-Lee. The two were colleagues at CERN where the WWW was born. Cailliau, along with Nicola Pellow, also created the first web browser for the Macintosh system called MacWWW (also known as Samba). The program was sold for 50 European Currency Units making it the first commercial web software.
Robert Cailliau has also designed the logo of the World Wide Web. At the first international WWW Conference in 1994, all six inductees were presented a Chromachron watch with the logo.