Glossary
What is First-party data?
Also called: 1P data, publisher first-party data
First-party data is information a publisher collects directly from its own audience, such as sign-ups, logins, reading history and survey answers.
हिंदी में पढ़ेंFirst-party data comes from your own site or app: newsletter sign-ups, logged-in accounts, the articles people read, survey answers and purchases. Third-party data, by contrast, is collected by other companies across many sites, usually with cross-site cookies and pixels, and sold as audience segments.
First-party data works where third-party cookies do not, because it comes from your own relationship with the reader. With consent, it powers logged-in IDs, private deals and curated audiences. The IAB’s Curated Audiences standard, formerly Seller Defined Audiences, lets you send a standard segment label, such as Audience Taxonomy ID 372 for desserts and baking, in the bid request’s user.data without any user ID.
Consent still applies. Prebid’s documentation notes that supplying first-party user data may require special consent in some regions, and not every bid adapter reads every convention. Start by listing what your site genuinely knows about readers, then map it to standard taxonomy IDs.
Example
Say a recipe site has 200,000 newsletter subscribers and 40,000 logged-in accounts: up to 240,000 known readers if no one is in both. A reader who has read 6 baking recipes this week can be sent as segment 372 without any user ID, so the label works on any browser.
Why it matters to publishers
Buyers pay for signals they can trust, and first-party signals work across browsers. They hold their value however cookie policies change.