Guardian News & Media has appointed Teads to provide its outstream video advertising in the UK and Europe.
The deal will enable the publisher of The Guardian to increase its video and display ad monetisation through both its direct sales team as well as through Teads.
It will cover ad inventory on browsers on mobile and desktop, before extending to in-app advertising later in 2019.
Outstream ads, which Teads defines as "inRead", are one of the fastest-growing areas of video advertising, generating £900m in the UK, according to the Internet Advertising Bureau’s 2017 Digital Adspend Report.
The ads appear seamlessly in an article and auto-play, but do not "pop up" or block the screen, making them less invasive.
Teads also currently works with the BBC, Vice, and Daily Mirror publisher Reach.
The company launched a suite of inRead products in 2017 offering video and display ad inventory across devices.
Products such as inRead Scroller, Canvas, Swing, Slideshow and Carousel are placed into editorial content and are "viewable by design". This allows advertisers to run sequential targeting campaigns across both display and video with the same platforms.
Hamish Nicklin, chief revenue officer at The Guardian, said: "InRead video and display provides advertisers and publishers with engaging, creative and non-intrusive ad formats. We’re happy to be working with Teads as part of our overall strategy to ensure brands have access to our quality environment and progressive audiences."