What is first-party data?
Why does first-party data matter for ads?
Because it is the data you can send to ad platforms from your own systems, rather than buy from someone else. For personalised ads on Google Search, Gmail and YouTube, Google allows "using first-party data to create audiences for ads targeting"1. Third-party data may only segment those first-party audiences, not build audiences on its own1.
In practice, first-party data feeds three things:
- Audiences. Customer lists for targeting or exclusion.
- Conversion matching. Enhanced conversions send hashed customer data, such as an email address, to Google to match conversions better.
- Server events. Server-side tracking passes data from a server you control. Meta scores how well that data matches its accounts with Event Match Quality.
Each of these raises a consent question. Consent Mode passes the visitor's choices to Google tags, which change what they send. What you may collect and share is a legal question: your counsel decides.
Our view: first-party data is plumbing, not a strategy. Checking what actually reaches each platform belongs in an ecommerce tracking audit.
Zero-party data vs first-party data: what is the difference?
Zero-party data is a term coined by Forrester Research, according to a CRM vendor's guide2. The guide quotes the definition: zero-party data is "that which a customer intentionally and proactively shares with a brand", for example through a preference centre2. In the same vendor's framing, first-party data is observed behaviour, while zero-party data is what the customer tells you outright2.
The vendor presents them as separate types2. Our view: treat zero-party data as a subset with a label, not a separate pile. A quiz answer is still data you collected yourself.
Easily confused with
First-party data vs Third-party data
Google's policy calls it "user information that you purchase or otherwise obtain from other sources"1.
First-party data vs Second-party data
A 2019 post on an industry body's blog describes it as "someone else's first party data", made available for a defined purpose under a contractual agreement3.
Buzzword alert
"We'll build your first-party data strategy"
Usually means: customer lists, server events and enhanced conversions, which are setup work with a consent question attached.
Ask: which number should change once it is in place, and how will we measure it?
FAQ
Is first-party data the same as 1P data?
Yes. "1P data" is shorthand for first-party data.
Does owning first-party data mean consent is covered?
No. Collecting data and using it for ads are separate questions. Which consent you need is for your counsel to decide.
Is a bought email list first-party or third-party data?
Third-party, under Google's definition, because you obtained it from another source1. A list you collected from your own customers is first-party data.
Let’s find what’s actually working.
Next step. See how cleaner data changes the numbers you report. Use the Is your ROAS real? calculator.