Legitimate interests
In practice, for a UK buyer
The paragraph above is the neutral answer. This is the part a vendor glossary leaves out.
The basis most advertising targeting actually relies on, and the one most often asserted without the assessment that makes it valid. AdBuyMCP attaches a standing condition to every legitimate-interest source stating that an assessment must be on file for it — which is a statement of what you owe rather than confirmation that it exists.
What this one connects to
Most confusion in media buying comes from two adjacent terms being used interchangeably, so these are the neighbours worth reading next.
Lawful basis
The legal ground relied on to process personal data, of which six exist under UK GDPR and at least one must be identified before processing begins. In advertising the two that matter are consent and legitimate interests, and the basis has to be settled before the processing, not after.
Legitimate Interests Assessment (LIA)
The documented three-part test of purpose, necessity and balancing that underpins any reliance on legitimate interests. It must be completed and retained before an organisation may rely on legitimate interests as its lawful basis for processing personal data.
UK GDPR
The United Kingdom's data protection regime, retaining the structure of the EU General Data Protection Regulation. Requires a lawful basis for processing personal data and gives individuals rights over data about them.
Consent
A freely given, specific, informed and unambiguous indication that someone agrees to their data being processed. Must be as easy to withdraw as to give, and cannot be inferred from silence or inactivity.
More on compliance and clearance
UK data protection and UK advertising clearance: what has to be true before an ad runs.
45 minutes. Bring a real brief and we compile it live. You describe one audience and watch it compile into seven targeting specifications, each with the score for how much of the definition survived.
Talk it through