Microsoft plans to turn on the Windows Update spigot for Internet Explorer 9 (IE9) on Monday, April 18.
Starting then, Windows Vista and Windows 7 PCs will begin to automatically offer users the upgrade, Microsoft said Thursday.
"IE9 will not install automatically on machines," Roger Capriotti, who heads IE marketing at Microsoft, said in a blog post. "Users will have to agree to install IE9."
Windows XP users will not see the IE9 upgrade offer or be allowed to install the browser because IE9 does not work on that still-dominant operating system. The newest browser suitable for XP is 2009's IE8.
When the IE9 upgrade is offered to users running IE7 or IE8 on Vista or Windows 7, a splash screen will appear that lists three choices: Install the browser, decline IE9 or delay the upgrade. If the user chooses the last, IE9 will be offered again at a later date.
As it typically does with major upgrades for its browsers and operating system service packs, Microsoft will gradually throttle up the offer; not everyone will be presented with IE9 immediately. Microsoft plans to wrap up the upgrade program by the end of June.
Business PCs managed by IT administrators who push patches and upgrades with Windows Server Update Services will not be affected by the offer until June, when Microsoft first makes IE9 available via WSUS, said Capriotti. Corporations can also deploy a blocking toolkit to insure that IE9 doesn't make it onto company PCs via Windows Update.
Vista and Windows 7 users have been able to manually download and install IE9 since its mid-March launch.
Microsoft delayed the release of the Japanese edition of IE9 because of the earthquake and tsunami that hit the country three days before the browser's launch. On Thursday, Capriotti said Microsoft will release the Japanese version on April 25, and add it to Windows Update sometime later.
The company also confirmed that it will provide IE9 security updates throughout the support lifecycles of the four editions of Windows that run the browser.
"IE9 ... will be supported for the entire life of ... Windows 7, Windows Vista, Windows Server 2008 and Windows Servicer 2008 R2," a company spokeswoman said.
Historically, Microsoft has tied browser support to Windows; when a version of Windows exits support, so does any browser that runs on that edition. Microsoft will patch IE8 on Windows XP, for example, through April 2014 -- when XP drops off the support list -- even though IE8 wasn't the browser that shipped with the 10-year-old OS.
Microsoft's commitment means that Vista Home Basic, Home Premium and Ultimate users will receive IE9 security updates through April 2012, when those editions exit support. Corporate users running Vista Business or Vista Enterprise will see IE9 patches through April 2017.
Meanwhile, Windows 7 Starter, Home Basic, Home Premium and Ultimate users can expect to receive IE9 security updates through January 2015, while Professional and Enterprise users will get patches through January 2020.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer or subscribe to Gregg's RSS feed . His e-mail address is email@example.com.