What is CMP (consent management platform)?

A consent management platform shows the privacy banner and records what each reader agrees to, such as storing data on their device or personalised ads, and which vendors may do it. Under the IAB Europe Transparency and Consent Framework (TCF), the CMP writes these choices into a TC string; for US privacy laws it can write a GPP string. Prebid and other ad tech then attach the string to every bid request.

For Google demand in the EEA, the UK and Switzerland, which CMP you use matters. Google has required a Google-certified CMP integrated with the TCF for personalised ads since January 2024 in the EEA and UK, and since July 2024 in Switzerland. Registered with IAB Europe is not the same as Google-certified. Traffic from a non-certified CMP may get only non-personalised or limited ads, and limited ads use no cookies or IDs for ads, so most frequency capping stops.

Google also treats TCF v2.3 as mandatory for TC strings created from 1 March 2026. Check that your CMP is on Google’s certified list, covers web, apps and CTV if you run them, and writes v2.3 strings. This is general information, not legal advice.