Garrett Sloane reports for AdAge that Instagram has revealed how ads inside the Stories section for the first time will work.

The new ads take up the full vertical screen between different users' posts, and are similar to Snapchat ads, but longer - up to 15 seconds. Sponsored photos display for 5 seconds and are instantly skippable.

Instagram said in a blog post:

"Ads in Stories will let you use targeting, reach and measurement capabilities that make your ads personally relevant to the people you want to reach."

Sloane points out that a chief advantage of Instagram over Snapchat is in the areas of ad technology and data targeting, since Instagram is built on top of Facebook and thus benefits from insights gained from FB's 2B monthly users.

Major brands that tested the new ads include Nike, Buick, Netflix, Airbnb and ASOS.

These ads are entertaining but stealthy - see the very tiny font in which "ASOS" appears in their ad here.