Mosaic was the first popular World Wide Web browser and Gopher client. It was reliable and easy to install, which opened the Web up to the general public. Mosaic was the first browser to actually implement images embedded in the text, instead of displayed in a separate window.

Mosaic was developed at the National Center for Supercomputing Applications (NCSA) beginning in late 1992. NCSA released the browser in 1993, and officially discontinued development and support on January 7, 1997. However, it can still be downloaded from NCSA.

Background

Marc Andreessen and Eric Bina originally designed and programmed NCSA Mosaic for Unix's X Window System at NCSA. Funding for the development of Mosaic came from the High-Performance Computing and Communications Initiative, a program created by the High Performance Computing and Communication Act of 1991 (or The Gore Bill after its author, then-Senator Al Gore).

Development of Mosaic began in December 1992. Version 1.0 was released on April 22, 1993, proceeded by two maintenance releases during summer 1993. A port of Mosaic to the Commodore Amiga was available by October 1993. Version 2.0 of NCSA Mosaic was released in December 1993, along with version 1.0 releases for both the Apple Macintosh and Microsoft Windows. An Acorn Archimedes port was underway in May 1994."Spinning" NCSA Mosaic logo depicting linked nodes across the world

The licensing terms for NCSA Mosaic were generous for a proprietary software program. For all versions non-commercial use was typically free (with certain boundaries). In addition the X Window System/Unix version publicly provided source code (source code for the other versions was available after agreements were signed). Despite persistent rumors to the contrary, however, Mosaic was never released as open source software during its brief reign as a major browser; there were always constraints on permissible uses without payment.

Marc Andreessen, the leader of the team that developed Mosaic, left NCSA and, with Jim Clark, one of the founders of Silicon Graphics, Inc. (SGI), and four other former students and staff of the University of Illinois, started Mosaic Communications Corporation. Mosaic Communications eventually became Netscape Communications Corporation, producing Netscape Navigator.

Spyglass licensed the technology and trademarks from NCSA for producing their own web browser but never used any of the NCSA Mosaic source code. Microsoft licensed Spyglass Mosaic in 1995 for US$2 million, modified it, and renamed it Internet Explorer. After a later auditing dispute, Microsoft paid Spyglass $8 million. The 1995 user guide The HTML Sourcebook: The Complete Guide to HTML, specifically states in a section called Coming Attractions, that Explorer "will be based on the Mosaic program" (p. 331). Versions of Internet Explorer before version 7 stated "Based on NCSA Mosaic" in the About box. Internet Explorer 7 was audited by Microsoft to ensure that it contained no Mosaic code, andthereforeno longer credits Spyglass or Mosaic.

Immediate Impact

Screenshot of original 0.6 beta for Windows

Other browsers existed during this period, notably Erwise, ViolaWWW, Midas, and Cello. These browsers, however, would not create the same impact as Mosaic upon public use of the Internet.

In the October 1994 Issue of Wired, Gary Wolfe notes in the article, "The (Second Phase of the) Revolution Has Begun: Don't look now, but Prodigy, AOL, and CompuServe are all suddenly obsolete - and Mosaic is well on its way to becoming the world's standard interface":

Importance of Mosaic

Plaque commemorating the creation of Mosaic web browser by Eric Bina and Marc Andreessen, new NCSA building, University of Illinois at Urbana-Champaign.

Scholars consider Mosaic to be the web browser which led to the Internet boom of the 1990s. Robert Reid underscores this importance stating, "while still an undergraduate, Marc wrote the Mosaic software ... that made the web popularly relevant and touched off the revolution" (p.xlii). Reid notes that Andreessen's team hoped:

to rectify many of the shortcomings of the very primitive prototypes then floating around the Internet. Most significantly, their work transformed the appeal of the Web from niche uses in the technical area to mass-market appeal. In particular, these University of Illinois students made two key changes to the Web browser, which hyper-boosted its appeal: they added graphics to what was otherwise boring text-based software, and, most importantly [sic], they ported the software from so-called Unix computers that are popular only in technical and academic circles, to the Microsoft Windows operating system, which is used on more than 80 percent of the computers in the world, particularly personal and commercial computers. (p.xxv).

It should be noted that Mosaic was not the first PC browser; this was Tom Bruce's little-known Cello. The UNIX version of Mosaic was already making it famous before the PC and Mac versions came out. Other than displaying images embedded in the text instead of in a separate window, Mosaic did not in fact add many features to the browsers it was modelled on, like ViolaWWW. But Mosaic was the first browser written and supported by a team of full-time programmers, which was reliable and easy enough for novices to install, and the inline graphics proved immensely appealing. Mosaic made the Web accessible to the ordinary person for the first time.

Reid also refers to Matthew Gray's well-respected website, Internet Statistics: Growth and Usage of the Web and the Internet, which designates a dramatic leap in web use around the time of Mosaic's introduction (p.xxv).

In addition, David Hudson concurs with Reid, noting that:

Marc Andreessen's realization of Mosaic, based on the work of Berners-Lee and the hypertext theorists before him, is typically recognized as the beginning of the web as it is now known. Mosaic, the first web browser to win over the Net masses, was released in 1993 and made freely accessible to the public. The adjective phenomenal, so often overused in this industry, is genuinely applicable to the...'explosion' in the growth of the web after Mosaic appeared on the scene. Starting with next to nothing, the rates of the web growth (quoted in the press) hovering around tens of thousands of percent over ridiculously short periods of time were no real surprise (p.42).

Ultimately, web browsers such as Mosaic became the killer applications of the 1990s because they were the first programs to give a multimedia graphical user interface to the Internet's burgeoning wealth of distributed information services (formerly limited to applications such as FTP, Usenet and Gopher). This was also a time when access to the Internet was expanding rapidly outside its previous domain of academia and large industrial research institutions.

End of Mosaic

Mosaic's popularity as a separate browser began to lessen upon the release of Andreessen's Netscape Navigator in 1994. As Ian S. Graham notes in the section called "Coming Attractions" in The HTML Sourcebook: The Complete Guide to HTML, "Netscape Communications has designed an all-new WWW browser Netscape, that has significant enrichments over the original Mosaic program" (p. 332).

By 1998 its userbase had almost completely evaporated. After NCSA stopped work on Mosaic, development of the NCSA Mosaic for the X Window System source code was continued by several independent groups. These independent development efforts include mMosaic (multicast Mosaic) which ceased development in early 2004 and VMS Mosaic which is under active development as of November 2007.