Released in 1991, Viola was the invention of Pei-Yuan Wei, a member of the eXperimental Computing Facility (XCF) at the University of California, Berkeley. Viola was a UNIX-based programming/scripting language; the acronym stood for "Visually Interactive Object-oriented Language and Application".
Pei's interest in graphically based software began with HyperCard, which he first encountered in 1989. Of that, Pei said, "HyperCard was very compelling back then, you know graphically, this hyperlink thing, it was just not very global and it only worked on Mac ... and I didn't even have a Mac". Only having access to X terminals, Pei, in 1990, created the first version of Viola for such terminals: "I got a HyperCard manual and looked at it and just basically took the concepts and implemented them ..."
Pei released Viola 0.8 in 1991.
After graduating, Pei developed Viola further while working with the XCF and startups. Later, he would be funded by O'Reilly Books, the technical publisher, which used the software to help demonstrate its Global Network Navigator site. His major goal was to create a version of Viola for the Internet:
X-Window was a Unix-based system so it had TCP/IP built in and the Internet was a logical step. The question was how to transport his Viola pages across the Internet. He was on the verge of an independent invention of networked hypertext. 'And that's when I read Tim's e-mail about the World Wide Web' he explains. 'The URL was very, very clever, it was perfectly what I needed. He dropped Tim a line saying that he was thinking of writing a browser for X. 'Sounds like a good idea,' said Tim in a reply posted to www-talk on 9 December. Four days later, Pei Wei told www-talk that he had made a browser.