Consent string

A consent string is a compact, encoded record of a user's privacy choices, generated by a consent management platform and passed through the advertising chain, that tells each vendor which purposes the user has consented to or objected to and under which legal basis.

Two formats are in use. The TCF TC string, defined in IAB Europe's framework, encodes the version, creation and update timestamps, the consent management platform, the Global Vendor List version, purpose consents, purpose legitimate interests, vendor consents, vendor legitimate interests, publisher restrictions and, in v2.3, disclosed vendors (IAB Europe, TCF; TCF technical specifications on GitHub). The Global Privacy Platform (GPP) string, defined by IAB Tech Lab, is a container that carries sections for multiple jurisdictions, including TCF for the EU and the US state privacy sections, with a header that lists which sections are present (IAB Tech Lab, GPP Consent String Specification). IAB Tech Lab updated GPP and released DDRF v2 on 23 October 2025 (IAB Tech Lab, 23 October 2025).

In OpenRTB the GPP string goes in regs.gpp with the applicable section IDs in regs.gpp_sid, and the TC string in user.consent (OpenRTB 2.6, sections 3.2.3 and 3.2.20). A bidder must parse the string on every request, which is a QPS cost, and must log what it saw, which is a compliance cost; the consent string is also what the IAB Tech Lab Agent Registry ties to a company's GPP ID when an agent is registered (IAB Tech Lab, Agent Registry).

Example: "regs": { "gpp": "DBABMA~CPXxRfAPXxRfAAfKABENB-CgAAAAAAAAAAYgAAAAAAAA", "gpp_sid": [2] } is a GPP string whose header (DBABMA) announces one section, section 2 (TCF EU), followed by the TC string.

Related: TCF, bid request, UID2, MHMDA.

Source: IAB Europe, TCF technical specifications; IAB Tech Lab, Global Privacy Platform Consent String Specification; OpenRTB 2.6.

1. IAB Europe, TCF
2. TCF technical specifications on GitHub
3. IAB Tech Lab, GPP Consent String Specification
4. IAB Tech Lab, 23 October 2025
5. OpenRTB 2.6, sections 3.2.3 and 3.2.20