Google's introducing three new ad formats for AdSense, its ad placement service that serves millions of advertisers globally. The new formats are "native" ad formats, meaning they are highly customizable to match the look and feel of a publishers' content, and are very mobile-friendly.

From a user perspective, native formats can make for a less intrusive experience, although can sometimes be confused with content if not properly labeled. From a publisher perspective, the updates will make it easier to create ads for different screen sizes.

Why it matters: Google has been aggressively pushing efforts to improve the user ad experience on its platform, including these new ad units, but some search engine optimization experts argue the changes will only further bury publishers' organic content on its platform.

"Many of Google's algorithm changes this year have negatively impacted the traffic to websites with quality issues," says Len Raleigh, CEO at SEO and content marketing strategy firm Telapost. "Used excessively, I believe the new AdSense ads could potentially cause quality issues on publisher's pages, leading to a loss of traffic."

More about the new formats below.

• In-feed: Ads that fit neatly inside publishers' feeds. (Feeds are lists of articles or products on a websites.) These ads can be customized to match the look and feel of your content. (Available to all publishers)
• In-article: Native ads that run between the paragraphs of a publishers' page. These full-width ads are meant to help publishers monetize smaller screen spaces, making them ideal for mobile. (Available to all publishers)
• Matched content: A content recommendation tool that helps publishers promote content to visitors, to create additional revenue opportunities. (Available to some publishers)