Under the multiyear deals, Seattle-based RealNetworks would continue to offer the Google Toolbar with its RealPlayer, and would also offer people downloading the media player the option of downloading Firefox. Financial terms were not disclosed.
In addition, the toolbar and browser would soon be available to people downloading RealNetwork's Rhapsody music service client and RealArcade games.
RealNetwork says it distributes more than 2 million pieces of software a day worldwide. In its prior two-year agreement with Google, RealNetworks distributed "millions" of Google toolbars globally.
"Real has been one of Google's most important distribution partners for the past two years, and we are delighted to broaden and deepen that relationship," Eric Schmidt, chief executive of Google, said in a statement.
The deal could help Mozilla in its effort to grab market share from Microsoft's Internet Explorer, which dominates the browser market. Mozilla this week said it had passed the 200 millionth download of Firefox, which has grabbed 15 percent of the global usage share since its released 21 months ago. Much of that progress has come at the expense of IE, which has just under 80 percent of global usage.
Google, on the other hand, dominates the toolbar market with Yahoo Inc. Together, the companies accounted for more than 95 percent of the searches originating from toolbars in May, according to ComScore Networks. Google had 49.1 percent, and Yahoo, 46.2 percent.