The red banner reads "Earnings at risk — you need to fix some ads.txt file issues to avoid severe impact to your revenue," and it is one of the few AdSense warnings that means exactly what it says: leave it unresolved and Google will eventually stop bidding on your inventory. The good news is that the fix is a one-line text file, and nearly every case comes down to the same three mistakes — the file is missing, the publisher ID in it is wrong, or Google's crawler can't reach the file where it expects to find it. Here's the whole repair, in order.
What the warning actually means
Ads.txt ("Authorized Digital Sellers") is a plain-text file at your domain root that lists which ad systems are allowed to sell your inventory. AdSense raises the earnings-at-risk alert when a site linked to your account either has no ads.txt file or has one that doesn't include your account's publisher ID. That second case is the sneaky one: a file that exists but names the wrong pub ID — a leftover from a previous owner, an agency template, or another site's copy-paste — is treated as an explicit statement that your account is not authorized, which is worse than no file at all.
The one line that clears it
For AdSense, the required entry is a single line:
google.com, pub-XXXXXXXXXXXXXXXX, DIRECT, f08c47fec0942fa0
Replace the sixteen X's with your own publisher ID. Two details matter here. First, use your real pub ID — it's in AdSense under Account → Settings → Account information, or you can skip transcription errors entirely by clicking Fix now on the warning itself and downloading the file AdSense generates, which arrives pre-populated with the correct ID. Second, leave the last field alone: f08c47fec0942fa0 is Google's certification-authority ID and it is the same for every AdSense publisher — it identifies Google, not you. If other networks also sell your inventory, their lines live in the same file, one per seller.
Where the file has to live
Google's crawler starts at the root domain: yourdomain.com/ads.txt must either serve the file directly or redirect to wherever it lives. If your site resolves to www, that means setting up a redirect from domain.com/ads.txt to www.domain.com/ads.txt — a step that trips up more publishers than the file contents ever do. The file needs to return an HTTP 200; a 404 or an error page means the response is simply ignored, and Google recommends the file resolve over both HTTP and HTTPS. A subdirectory won't work, and a subdomain won't cover the root. If you're on a hosted platform where you can't just drop a file in the root, the same root-domain rule still applies — our guide to adding the AdSense ads.txt file to Shopify walks through the workaround for one popular case.
Verify it yourself before AdSense does
Don't wait for Google to tell you whether the fix worked. Open an incognito tab and load yourdomain.com/ads.txt directly: you should see plain text containing your pub- line, not a styled 404 page, not a redirect to your homepage, and not a file with smart quotes or stray HTML in it. Then check Sites in AdSense, where each domain shows its ads.txt status. If the file loads publicly with the right ID and a 200 status, the crawler side is done and the rest is waiting.
How long until the banner goes away
The alert does not clear on save. Google re-crawls ads.txt on its own schedule — expect the warning to persist for a few days up to about a week after a correct file is in place, and on low-traffic sites that make few ad requests it can take up to a month. There's a grace mechanism in the other direction too: if your file becomes temporarily unreachable, previously crawled entries are retained for up to five days before being purged, so a brief outage won't instantly de-authorize you. The practical rule: fix it once, verify the URL loads, then stop re-editing the file — repeated churn just resets your wait.
Make it part of the monetization checklist
Ads.txt failures are rarely dramatic; they're entropy. A site migration drops the file, a template swap overwrites the root, a "cleanup" deletes what looked like a stray text file — and revenue quietly erodes until someone notices the banner. Sites that treat monetization as an operations problem keep ads.txt on the same recurring checklist as analytics filters and consent tooling: one URL check, once a month, thirty seconds. It's the cheapest revenue insurance a content site can buy.