Update 10/02/2025: As noted by SteamDB on Bluesky, while this specific page on Steam's advertising policy is new, the policy itself is not. Valve has had a ban on these kinds of in-game ads in Steam games for the last five years at minimum, viewable on its pricing policy page.
Product placement is still in, so long as "such portrayals are not [[link]] disruptive and are appropriate within the context of the game." Valve gives a racing game with real life sponsors on the cars as one example of what's okay, and it sure sounds like my dream reboot of Pepsiman could still find a home on the store, thank god. Cross-promotions are allowed too, but Valve states "under no circumstances is it okay to charge developers to participate in a bundle or sell access to a store page or other page on Steam." Last, paid advertising campaigns outside Steam that lead to a store page are also fair game.
What's been banned is any form of in-game advertising that gates access to, or otherwise interferes with, gameplay. "Developers should not use paid advertising as a business model in their game, such as requiring players to watch or otherwise engage with advertising in order to play," Valve writes on the page. Basically, it sounds like a blanket ban on any sort of "watch this ad to play the game" design, and it also extends to in-game ads being tied to rewards like power ups or in-game currency.
I don't think I've ever encountered or heard of a single game engaging in this behavior on Steam, but given its prevalence on other platforms, particularly mobile games, it makes sense for Valve to lay this out as a more preventative measure. Valve is legendarily light touch when it comes to moderating Steam, but in addition to an "I'll know it when I see it" approach to banning offensive content, Valve has explicitly banned NFT and crypto-derived games, and also requires games relying on generative AI to disclose its use. The company clearly has a sense of what it wants PC gaming to look like as far as its influential platform goes.
