What is a consent string (TC string)?

A consent string is an encoded record of a visitor's consent choices that gets passed between a website's consent platform and its advertising vendors. In the IAB's Transparency and Consent Framework, it tells every vendor in the ad chain exactly which purposes and vendors the visitor agreed to.

What is inside it

The string encodes the visitor's decisions per purpose (like ad personalization or measurement) and per vendor, plus metadata such as when the choice was made and which banner version was shown. Vendors are required to read and respect it before processing data.

Why it matters for publishers

Ad partners check the consent string before bidding. A missing or malformed string means no personalization signal, which usually means lower-value contextual-only bids. Keeping the string accurate is both a compliance and a revenue concern.