--- title: "What is first-party data? | AdBuyMCP" description: "Data an organisation has collected directly from its own customers and visitors: a CRM list, purchase history, site behaviour." url: "https://adbuymcp.com/glossary/first-party-data" --- [Home](https://adbuymcp.com/) / [Glossary](https://adbuymcp.com/glossary) / First-party data Targeting and identity # What is first-party data? Data an organisation has collected directly from its own customers and visitors: a CRM list, purchase history, site behaviour. Distinguished from third-party data by the existence of a direct relationship with the person it describes. [Get my plan and price](https://adbuymcp.com/start) [Book a 30-minute call with the founder](https://adbuymcp.com/contact#book) Free, with no card. We read your homepage, draft who buys from you and show your monthly price before you join the waitlist. Nothing is bought until you've approved the plan and the ads. What it means here ## Here is what the term means for a UK buyer The definition above holds anywhere. Buying media in the UK adds the detail below, including where AdBuyMCP does something different. It is the most valuable targeting asset most advertisers own and the hardest to activate on premium channels, because getting a list from your database onto a television requires an identity bridge that keeps the list private. Consent-chained identifiers such as EUID are built to be that bridge. AdBuyMCP's compiled CTV plans carry an empty EUID audience list, so that bridge is designed and unused. The EUID client behind it is built, and it waits on an EUID participation agreement before any real identity goes through it. ## Where can you use first-party data in the UK? Social platforms make it straightforward, because they already hold matching identifiers for a hashed customer list. Connected TV, audio and out-of-home need an identity bridge that keeps the list private, which in the UK and Europe means a consent-based identifier derived from a hashed email or phone number, such as EUID. That route needs a participation agreement, and a configuration change will not stand in for one. The data is accurate because it comes from people you have a direct relationship with, and the terms on which they shared it limit what you can do with it. ## What should you check before a customer list leaves your hands? Check the terms on which your customers shared their data. Check which lawful basis each use relies on, and whether a legitimate interests assessment is on file where the basis is legitimate interests. And check what the receiving platform keeps, and for how long. AdBuyMCP's own rule is to hold hashed advertising identifiers for at most 90 days, after which the hash is stripped from the exposure event and the event is re-graded to a coarser key. Exactly one module in the product performs identity joins, the key-translation service, so the rule has one place to be enforced and one place to be audited. Read next - [First-party data in UK media buying Goes deeper](https://adbuymcp.com/guides/first-party-data-in-uk-media-buying) - [Streaming TV in an awareness plan Channel](https://adbuymcp.com/channels/ctv-streaming) - [What UK awareness advertising costs Cost](https://adbuymcp.com/cost) - [What a fidelity score measures Guide](https://adbuymcp.com/guides/what-a-fidelity-score-is) Type your company website or work email to see who we think buys from you and what reaching them 3, 5 or 12 times a week would cost. [Get my plan and price](https://adbuymcp.com/start) Free, with no card. Related terms ## These terms sit next to this one Most confusion in media buying comes from two adjacent terms being used interchangeably, so these are the neighbours worth reading next. - ### [Third-party data](https://adbuymcp.com/glossary#third-party-data) Audience data collected by one organisation and licensed to another for targeting, with no direct relationship between the licensee and the people described. Sold as segments through data marketplaces attached to buying platforms. - ### [European Unified ID (EUID)](https://adbuymcp.com/glossary#euid) A consent-based identifier for European advertising, derived from a hashed email or phone number provided with consent, designed to let first-party audiences be addressed across publishers without third-party cookies. - ### [Identity resolution](https://adbuymcp.com/glossary#identity-resolution) The process of deciding that two different identifiers refer to the same person or household, so that behaviour seen under one can be joined to the other. - ### [Lookalike audience](https://adbuymcp.com/glossary#lookalike-audience) An audience built by finding people who resemble a seed group (usually the advertiser's existing customers) on whatever signals the platform holds. The resemblance model is the platform's and is not disclosed. Same group ## These terms are also in Targeting and identity How an audience is described to a seller, and how much of the description survives. Most media-buying problems start at this translation step. - [Audience segment](https://adbuymcp.com/glossary/audience-segment) - [Contextual targeting](https://adbuymcp.com/glossary#contextual-targeting) - [Retargeting](https://adbuymcp.com/glossary#retargeting) - [Frequency capping](https://adbuymcp.com/glossary/frequency-capping) - [Deduplication](https://adbuymcp.com/glossary#deduplication) - [Experian Mosaic](https://adbuymcp.com/glossary#experian-mosaic) - [CACI Acorn](https://adbuymcp.com/glossary#caci-acorn) - [Mobile advertising ID (MAID)](https://adbuymcp.com/glossary/maid) [All 81 terms](https://adbuymcp.com/glossary)