It offers a platform that helps advertisers find and reach audiences—for example, consumers who are interested in buying a car—across TV inventory on different networks, and across both linear and digital viewing. Linear refers to the traditional style of TV viewing—watching shows on a certain channel at a scheduled time—while digital includes streaming platforms.

Last year OpenAP introduced a so-called identifier to help advertisers more efficiently place and measure ads across separate digital and traditional TV systems.

OpenAP said it expects marketers to buy $500 million of advertising through its platform in the fiscal year ending Sept. 20, 2022, up 140% over the previous year. The company said it works with more than 100 advertisers.

OpenAP’s current owners are Comcast Corp.’s NBCUniversal,

Fox Corp.

and

ViacomCBS Inc.

WarnerMedia LLC was a founding member but withdrew in 2019 after

AT&T Inc.

acquired its parent, Time Warner Inc.

(Fox and Wall Street Journal parent

News Corp

share common ownership.)

AT&T and Discovery last year agreed to combine their media assets into a new, publicly traded company, a deal that is expected to close this year.

Discovery, whose networks include HGTV, Food Network, Animal Planet and many others, already has a working relationship with OpenAP. The company began using OpenAP’s identifier in spring 2021 and worked with the group on the introduction of XPm, a way of measuring audiences across different platforms.

“We work with pretty much every national network out there. But we also have networks on the board and at an investor level that are much more involved from a strategic perspective and road map planning,” OpenAP Chief Executive Officer

David Levy

said. “I think there was a real interest to further [Discovery’s] involvement and get more deeply engaged in a lot of the strategic discussions that are going on. And we frankly needed and want that insight, because every network has a different combination of challenges.”

The companies declined to disclose the financial terms of the deal.

Jon Steinlauf,

chief U.S. advertising sales officer at Discovery, and

Jim Keller,

Discovery’s executive vice president of digital ad sales and advanced advertising, will join OpenAP’s board of directors.

Marketers are looking for ways to better buy across platforms and content publishers, Mr. Keller said.

“Instead of us sitting on the sidelines and letting other competitors set the road map of how that could work around data, privacy, technology, measurement, we wanted to be part and parcel of the conversation,” he said. “There’s been significant momentum around audience-based sales in the overall marketplace over the last two years or so. But over the last six months, you can’t have a conversation with somebody if you’re not talking about audience-based sales.”

Write to Megan Graham at megan.graham@wsj.com