Vendors & measurement
Invalid fourth-party call
What Google's rule says
Authorized Buyers states that the ad is disapproved because of a detected fourth-party call to an unapproved technology vendor. The closely related reason, invalid vendor, is worded almost identically.
What actually causes it
- A measurement or verification vendor that is not on Google's certified list.
- An approved vendor called from a domain other than the one they were certified under.
- A vendor added to the tag chain by an agency or a partner without the ad server owner knowing.
- A vendor whose certification lapsed while the campaign was running.
How to fix it
List every host the creative calls, then check each against Google's certified third-party ad serving vendor table. Remove or replace the ones that are not on it — there is no self-service route to approving a vendor from your side.
The part that is not obvious
Certification is granted to a specific domain, not to a company, which is the detail that makes this reason recur on campaigns that have already fixed it once. A vendor can be certified and still trigger the violation because the tag calls a regional, legacy or CDN hostname that was never registered under the certification. The remedy is to compare the exact hosts in the network log against the table, rather than to check whether the vendor's name appears on it.
Related reasons
Reason name verified against Certified third-party ad serving vendors — Google on 30 July 2026. The causes and fix above are practitioner guidance, not Google policy text.