For five years, YouTube's skippable TrueView ads have let people push past an advertiser's spot to get to the videos they want to watch without brands being charged for the slight. Now the Google-owned video service has come up with a new way for advertisers to keep viewers' attention -- and for YouTube to keep advertisers' money.

YouTube is adding interactive cards to its TrueView video ads, so that marketers have the option to include more information as overlays atop their in-stream spots. These cards also give YouTube another way to make money from the ads even if people skip the full spot.

"We're trying to make TrueView an even better creative canvas for brands. Video has always had sight, sound and motion…. We're taking the next step and going deeper into interactivity," said Phil Farhi, director-product management for YouTube Ads.

Advertisers' TrueView cards can contain information about the brand or its products, a list of related videos or playlists from the advertiser and -- sometime in the next several weeks -- links to the advertiser's website.

YouTube has let advertisers append extra information atop their video ads before. However those so-called "annotations" only worked when watching YouTube on a desktop computer or laptop and were limited to text. TrueView cards work on tablets and smartphones and eventually internet-connected TV devices like Apple TV and Google's Chromecast. And they appear to be more visually appealing than annotations because they can contain images and resemble the informational cards that are part of the Google Now virtual assistant service.

Card overload, however, could obscure an advertiser's actual ad. Mock-ups of the TrueView cards provided by YouTube show that the cards appear as a scrollable vertical section that takes up about a quarter of the video player's real estate.

YouTube has one measure in place to make sure that ads aren't initially cluttered with cards. Cards won't automatically appear when a card-enabled Trueview ad plays. People will have to click a button in the top-right corner of the video in order to show the cards before they can interact with them.

Mr. Farhi said he expects brands to adjust to the format and produce video ads that take into account the card overlays, as some have done with the skip button that appears on the right side of the frame.

Coinciding with the cards addition, YouTube is also changing up how it's charging advertisers for the TrueView ads. To date, marketers have only had to pay if people watched their full ad, or at least 30 seconds of it if it's a long spot. If people clicked to skip the ad after five seconds, then the advertiser didn't have to pay for the view -- and YouTube didn't make any money.

Mr. Farhi declined to say what percentage of people who encounter TrueView ads click to skip them. In 2011 YouTube claimed 15% to 45% of people stick around to watch the full ad, or at least 30 seconds of it. The number of advertisers that have run TrueView campaigns grew by 45% in 2014, according to YouTube.

With TrueView cards, YouTube is upping its chances of making money. Starting in May, if people click on any of the card elements -- including the clicking the button to initially display the card elements -- YouTube will count it as a paid view and charge the advertiser. The advertiser will even have to pay if, after clicking to show the card elements, someone clicked to skip the ad, Mr. Farhi said.

"The reason we are incrementing views when people click on cards is it's a clear signal the user is interested in that advertiser or brand. In a world where the ad is not interactive, the lack of a skip was the strongest signal that showed it was a good ad for the user," Mr. Farhi said.

If people don't click to pull down the cards, then the advertiser will only be charged if someone watches the full TrueView ad or at least 30 seconds of it.

Later this year YouTube plans to roll out customized cards for specialized uses, though Mr. Farhi declined to offer any details like types of uses or advertisers that the specialized cards would cater to. However YouTube already introduced one example last year when it added a way for mobile developers to drive app downloads using TrueView.