Unfortunately the integrated EU User Consent feature of AdSense, which uses Google's Funding Choices API to provide the Consent Management Platform, does not provide an automatic means to prompt for re-consent when the original consent captured in the TC String reaches 13 months old.
In the Funding Choices implementation the TC String is persisted as a data element in a cookie named FCCDCF, with the TC String itself containing the date that consent was provided. To maintain compliance with IAB's TCF v2 framework, when the AdSense API processes this string and discovers that consent has expired it records a policy violation ("Error 3.3") against the ad units and does not render them. But it does nothing to help resolve the situation beyond providing a somewhat opaque notice that there is an issues that may "affect your ability to serve ads to European users"!
Consequently, earnings will drop over time as an increasing proportion of visitors have TC Strings containing consent that is no longer compatible with the rendering of ad units.
To resolve this issue, the AdSense implementation can be preceded by the following JavaScript (amended to match the domain and path of the FCCDCF cookie for the site) that will extract the TC String from the Funding Choices cookie, parse out the consent date, and then erase the cookie if it determines that consent was provided more than 12 months ago.
<script>
// Delete the Funding Choices cookie if consent is more than 12 months old
try {
const nm = "FCCDCF"; // Match name of Funding Choices cookie
const dm = "mydomain.com"; // Match domain of Funding Choices cookie
const pa = "/"; // Match path of Funding Choices cookie
let tc = ('; ' + document.cookie).split('; ' + nm + '=');
if (tc.length === 2) {
tc = decodeURIComponent(tc.pop().split(';').shift());
tc = JSON.parse(tc)[3][0].substring(1,9);
tc = Uint8Array.from(window.atob(tc), (v) => v.charCodeAt(0));
let dt = (tc[0] * 2**28) + (tc[1] * 2**20) + (tc[2] * 2**12) +
(tc[3] * 2**4) + (tc[4] >> 4);
if (Date.now() / 1000 - dt / 10 > 86400 * 365)
document.cookie = nm + "=;path=" + pa + ";domain=" + dm +
";expires=" + new Date(0).toUTCString();
}
} finally {}
</script>
There's some things that might be improved in the above script — unless of course Google makes it entirely unnecessary by starting to act as a responsible CMP by automatically re-prompting for consent:
- It may be possible to call functions of the Funding Choices / TCF API to drive re-consent, rather that rely on deleting the cookie before the AdSense code is run. I haven't examined the API to see if this is possible.
- It may also be possible to lazy load the script by hooking it into the AdSense API as an early callback. Again, I haven't looked at the API to see if this is possible.
Any such improvements to the above script are welcome and I'm happy to maintain this answer.
