Google Analytics Data Stream
Definition
A data stream is a source of incoming data for a GA4 property. For a website, it is the web stream that provides a measurement ID such as G-XXXXXXXXXX.
Why It Exists
It connects a real data source to a Google Analytics property. A property can collect data from web, iOS, and Android streams.
How It Fits Into The System
The web stream is configured in Google Analytics and then installed in the site through the Google tag. In a Next.js app, that often means passing the measurement ID to a Google Analytics component.
Important Details
The data stream is not the same thing as the property. The property stores and reports data; the stream is one input channel.
Example
The personal site can use a web data stream with NEXT_PUBLIC_GA_ID=G-... to send page view events into the site property.