One ads.txt File, Always Current
A stale authorized-sellers file is worse than no file. Ours now redirects to a source that updates itself.
There is a particular kind of ad-tech failure that nobody notices for months. A publisher adds a new demand partner, the partner's line never makes it into the ads.txt file, and buyers quietly stop bidding on inventory they are no longer sure is authorized. Nothing breaks. Revenue just goes down.
The cause is almost always the same. The file is a copy. Someone pasted it in once, and the paste went out of date.
What we changed
As of this month, all three of our authorized-sellers files are redirects rather than copies:
/ads.txt and /app-ads.txt: Both point at the same list, maintained in its own repository and updated when the partner set changes. One list covers both paths, which is how the file was published on our previous site.
/sellers.json: Points at exchange.loyal.app, which serves it directly with the correct content type.
Follow any of those three URLs and you land on the current data, not a snapshot of what was true whenever a person last remembered to update it.
Why a redirect rather than a file
A copied file has to be kept in sync by hand, which means it will eventually be wrong. A 301 cannot drift. The buyer follows it and reads whatever is authoritative right now.
There is a second reason, and it is the reason this took a specific fix rather than a config change. Crawlers are not browsers. Our app blocks unrecognised browsers on normal pages, which is correct for a marketing site and completely wrong for a file that exists to be read by machines. These three routes bypass the application entirely, so an ad-network crawler is never asked to prove it is Chrome.
The wider point about supply paths
Full ads.txt and app-ads.txt enforcement is one of the few transparency claims a buyer can verify without asking anyone's permission. You can check ours right now, in a browser, in about four seconds. That is roughly the standard the whole supply chain should be held to.
If you are a publisher on the Exchange, nothing changes on your side. If you are a buyer, you have one less reason to wonder whether the path is what we say it is.
