A web browser is a software package that enables a user to display and interact with HTML documents hosted by web servers. It is the most commonly used kind of user agent. The largest networked collection of hypertext documents is known as the World Wide Web.
Web browsers communicate with web servers primarily using the HTTP protocol to fetch web pagess identified by their http:URL. HTTP allows web browsers to submit information to web servers as well as fetch web pages from them. The file format for a web page is usually HTML and is identified in the HTTP protocol using a MIMEcontent type. Most browsers natively support a variety of formats in addition to HTML, such as the JPEG and GIF image formats, and can be extended to support more through the use of plugins. Many browsers also support a variety of other URL types and their corresponding protocols, such as ftp: for FTP, gopher: for Gopher, and https: for HTTPS (a SSL encrypted version of HTTP). The combination of HTTP content type and URL protocol specification allows web page designers to embed images, animations, video, sound, and streaming media into a web page, or to make them accessible through the web page.
Early web browsers supported only a very simple version of HTML. The rapid development of proprietary web browsers (see Browser Wars) led to the development of non-standard dialects of HTML, leading to problems with Web interoperability. Modern web browsers (such as Internet Explorer, Mozilla, Opera, and Safari) support standards-based HTML and XHTML (starting with HTML 4.01), which should display in the same way across all browsers.
Some of the more popular browsers include additional components to support Usenet news and e-mail via the NNTP, SMTP, IMAP and POP protocols.
Tim Berners-Lee, who pioneered the use of hypertext for sharing information, created the first web browser, named WorldWideWeb, in 1990 and introduced it to colleagues at CERN in March 1991. Since then the development of web browsers has been inseparably intertwined with the development of the web itself.
Netscape released its flagship Navigator product in October 1994, and it took off the next year. Microsoft, which had so far missed the Internet wave, now entered the fray with its Internet Explorer product, hastily purchased from Spyglass Inc.
This began the browser wars, the fight for the web browser market between the software giant Microsoft and the start-up company largely responsible for popularizing the World Wide Web, Netscape.
The wars put the web in the hands of millions of ordinary PC users, but showed how commercialization of the internet could ruin standards efforts. Both Microsoft and Netscape liberally incorporated proprietary extensions to HTML in their products, and tried to gain an edge by product differentiation. The wars ended in 1998 when it became clear that Netscape's declining marketshare trend was irreversible. This was in part due to Microsoft's integrating its browser with its operating system and bundling deals with OEMs; the company faced antitrust litigation on these charges.
Netscape responded by open sourcing its product, creating mozilla. This did nothing to slow Netscape's declining marketshare. The company was purchased by America Online in late 1998. Mozilla has since evolved into a stable and powerful browser suite with a small but steady marketshare.
Opera, a speedy browser popular in handheld devices and in some European countries was released in 1996 and remains a niche player in the PC web browser market.
The Lynx browser remains popular in certain markets due to its entirely text-based nature.
While the Macintosh scene too has traditionally been dominated by Internet Explorer and Netscape, the future appears to belong to Apple's Safari which is based on the KHTML rendering engine of the open source Konqueror browser. Safari is the default browser on Mac OS X.
In 2003, Microsoft announced that Internet Explorer would no longer be made available as a separate product but would be part of the evolution of its Windows platform, and that no more releases for the Macintosh would be made.