ads.txt is read from the root domain of the site making the ad call, not from every subdomain. Embedded or iframed games typically rely on the host site’s ads.txt, or on MCM-provided lines if the game is monetized through a partner network.
At a glance
| Fact | Value | Source |
|---|---|---|
| ads.txt file location required by spec | domain root, /ads.txt | iabtechlab.com |
| app-ads.txt purpose vs ads.txt | covers app-store distributed apps | iabtechlab.com |
| ads.txt spec version supporting multiple domains | v1.1, owner/manager domains | iabtechlab.com |
ads.txt is a plain text file crawled from the root of the domain that actually calls the ad exchange – not from every subdomain that hosts content. If your game runs on play.yoursite.com but ad requests are made from yoursite.com’s ad tags, the file needs to sit at yoursite.com/ads.txt. Subdomains generally need their own ads.txt only if they independently make ad requests under their own hostname; the IAB Tech Lab’s ads.txt v1.1 added owner and manager domain fields specifically to handle these multi-domain and reseller situations.
If you’d rather not manage ad tags, ads.txt and embedding logistics yourself, sites can instead embed a catalog of games through Playgama Partners with one line of code and no hosting; monetization and placement are handled on Playgama’s side.
Embedded or iframed games are trickier: crawlers read ads.txt from the top-level page domain, not from the iframe’s source domain, so a game embedded via iframe on a third-party site is generally covered by that site’s ads.txt, not the game’s own. If you distribute your game to other sites for embedding, each host site needs correct ads.txt entries for whichever network serves ads on that page.
What if i’m in an MCM (Multiple Customer Management) relationship?
If a parent network manages your inventory or account under Google Ad Manager’s MCM, add the exact ads.txt lines your MCM partner gives you to every site included in the program; Google does not publish fixed traffic thresholds for joining MCM (Google Ad Manager: About MCM).
Check first: which domain actually fires the ad request, then confirm that exact domain publishes ads.txt with the right seller lines.
Sources
- IAB Tech Lab: ads.txt
- Google Ad Manager: About MCM
- Google Ad Manager: MCM Manage Inventory
- Google Ad Manager: MCM Manage Account
Related questions
Does every subdomain need its own ads.txt file?
Only if that subdomain independently makes ad requests under its own hostname. Otherwise the root domain’s ads.txt, read by the crawler, is what matters.
Does ads.txt cover games embedded via iframe on another site?
Crawlers check the top-level page domain’s ads.txt, not the iframe source’s domain, so the host site’s ads.txt applies to embedded games.
Last updated: 24 September 2026