Yahoo has become the latest company to provide developers with the opportunity to build rich Internet applications with some desktop functions after it unveiled a preview offering known as BrowserPlus.

The new Yahoo tool will compete with other recently unveiled offerings, including Microsoft's Silverlight, Adobe Systems' Adobe Integrated Runtime, or AIR, and Prism from the Mozilla Foundation.

The software, which in this so-called "sneak peek" release only works on Yahoo sites, helps developers build applications that allow users to do things like drag-and-drop from the desktop, easily upload files and receive native desktop notifications while inside the browser, Yahoo said. Yahoo said the preview version, which was developed by a small team over the past year, will let it gain input from developers.

The final version of the software will support any website, Yahoo said. It did not say when the final version of BrowserPlus will be available.

The most unique feature of the software, according to Yahoo, allows users to add new services without having to restart a browser or reload a page. "For users, this means no more interruptions or installers to run," Yahoo said in a blog post.

"We handle the complexity of software distribution and updates. For developers, it means you can check for and activate new services with a single function call (pending user approval, of course). BrowserPlus is dynamic, allowing us to implement the standards of tomorrow while enabling fun and playful web applications along the way.

Yahoo said all updates are signed and verified by Yahoo so users can trust that they're are authentic. Updates are never applied without a user's approval. BrowserPlus will never let sites access a user's data or resources unless the user approves. If a security issues is found in a service on the Web, Yahoo said it can quickly deactivate that service so it can't be exploited.

As for performance, BrowserPlus runs separately from the browser so that Yahoo can minimize the performance impact and shut down the software when it is not needed. As a result, the software is unlikely to affect speed or stability of daily browsing, Yahoo said.