Yesterday, Valve made waves when it updated its Steamworks Documentation now to include a dedicated "Advertising on Steam" page, illuminating its anti-advertising-on-Steam stance— GamingOnLinux proceeded to report on this as a new policy. Still, this was just a dedicated page for an existing policy, as noted by SteamDB and later GamingOnLinux when it realized its error.
In any case, making and dropping a dedicated page just for this question communicates the restrictions more clearly and helps ensure that developers don't think they can get away with posting ad-laden, mobile game-esque slop on Steam. While the little regulation on Steam still allows for a lot, the most common freemium models from mobile gaming still are not welcome on the platform.
The official page under "Not Supported" states:
"Developers should not utilize paid advertising as a business model in their game, such as requiring players to watch or otherwise engage with advertising in order to play, or gating gameplay behind advertising. If your game's business model relies on advertising on other platforms, you will need to remove those elements before shipping on Steam. Some options you could consider include switching to a single purchase 'paid app,' or making your game free to play with optional upgrades sold via Microtransactions or Downloadable Content (DLC)."
Other behaviors considered "Not Supported" on Steam include using "advertising as a way to provide value to players, such as giving players a reward for watching or engaging with advertising in their game" or charging "other developers for access to Steam features. These include sale pages, bundles, store pages, franchise pages, etc.".
A limited degree of advertising is still allowed on Steam and listed as "Supported." Still, these all describe your more typical product placements, cross-promotions, and paid ads for games available on Steam outside of Steam. Of course, advertising is a part of any publisher or developer's toolkit— it's just unacceptable as a core tenet of gameplay, as Valve has now made it extra clear by setting aside a dedicated page on the matter.
Previously, this information was relegated to a few brief FAQs on the existing "Pricing" documentation page. The relevant FAQs state:
"Steam does not support paid ads or referral/affiliate revenue from showing ads for other games and/or products or services. If your game's revenue relies on advertising on other platforms, you will need to find a new monetization model in order to release on Steam. Some options you could consider: Switch your game be a single purchase or make it free to play with microtransactions or additional content as DLC" and "Steam does not support models where a customer is blocked and needs to pay to continue playing. If you would like to have a free demo to show off your game, you're welcome to do so. Your demo and full game can share files as well to continue game play. To figure out if a demo is the right thing for your game, please check out the Demos Documentation".
To those who have monitored Valve or used Steam frequently over the years, these policies shouldn't be much of a surprise. Mobile titles with these business models that make their way to Steam inevitably change to either a one-time purchase or a more palatable Free-To-Play model, in line with titles that pioneered that model for PC players, like Valve's own 2007-launched, 2011-turned-live-service, Team Fortress 2.
As noted by GamingOnLinux in its coverage, Valve has also long banned games reliant upon blockchain technologies, including crypto and NFTs, being sold on Steam. Considering how often these ventures (particularly NFTs) end up being outright scams, this is still a very wise policy on their part, but it, of course, does not stop the likes of studios like Ubisoft from self-publishing abhorrent NFT-RPGs, either.
