Google is testing a new advertising format that it hopes will make people spend more time looking at ads online, and even embed them in their own Web sites.

Called Gadget ads, the service has already been in testing with a small handful of clients. On Wednesday Google announced that it was widening the tests considerably, which means more of the ads will start appearing on Web sites.

The format allows companies to build ads that include audio, video, games, and live data feeds, and to spruce them up with the Flash and JavaScript programming languages. The ads wind up looking like small Web pages within a Web page, and people can save them to a blog or to their iGoogle home page.

Google posted several examples of the Gadget ads on its Web site. An ad for a Nissan car lets people type a U.S. postal code in the advertisement to get a map showing traffic conditions where they live. Another for the Six Flags theme park includes a simple game and a link to "add to your Google home page."

The ads give advertisers detailed metrics about who uses them, according to Google. The Six Flags ad delivered 94.5 million impressions to 17.1 million unique users, and was interacted with about 200,000 times, Google said.

According to Google, 0.3 percent of those exposed to the Gadget ads interacted with them. In comparison, direct mail generates a response rate of 2.18 percent, according to figures for 2006 from the Direct Marketing Association.

The Gadget ads run on Google's AdSense advertising network and are priced by number of clicks or number of impressions. Google didn't say when the testing period would end, but it said Gadget ads will eventually be available in 20 languages and 100 countries.

Microsoft and other companies also let advertisers put video and interactive features in Web sites, but Google claims that its ads offer more ways to keep people engaged. The ads can also appear on YouTube, and sellers can include part of a checkout process in the advertisement.