GA4: how to get data into a data stream

Getting data into GA4 in 2026 means: open the property, create or open a data stream under Admin, then install the Google tag or wire GTM. The old Universal Analytics connected-site-tag path is legacy. It stays below only if you still have a UA property hanging around.

Open GA4: https://analytics.google.com/.

The live path: GA4 Admin, Data streams

1. Open or create a GA4 property.
2. Bottom left, Admin (gear).
3. Under Property, click Data streams.
4. Open the web stream, or Add stream for a new one (site URL, stream name).
5. Copy the Measurement ID (G-XXXXXXXX).
6. Under Tagging instructions, install the Google tag (gtag.js), or bind the same stream in Google Tag Manager as a Google tag / GA4 Configuration tag.

Then load the site and check Reports or DebugView for page_view and session_start. Without an installed tag the stream stays empty, no matter how tidy the property looks.

Data retention before you explore

Under Admin, Data settings, Data retention, set how long event-level data is kept. GA4 offers shorter and longer windows. If you need explorations across many months, pick the longer window and save. Otherwise raw event data for explorations leaves the lookback earlier, even when aggregates remain in standard reports.

Legacy: connected site tags through a UA property

Universal Analytics stopped processing new hits on 1 July 2023. Connected site tags were the dual-tagging trick from the migration years: an existing UA-controlled gtag.js on the page could also send events to a GA4 property without a new snippet.

If you still have a UA property and need to reconstruct that old path:

1. Open the UA property.
2. Admin, Tracking Info, Tracking Code.
3. Scroll to Connected Site Tags and open it.
4. Paste the GA4 Measurement ID and click Connect.

That is archive knowledge for old installs, not a setup for new sites. Fresh measurement belongs in the data stream, not in UA.

Quick check before you call it done

• Right property and right stream?
• Measurement ID on the page or in the GTM container?
• Realtime or DebugView showing events from your visit?
• Data retention set on purpose?

If Realtime stays empty: tag blocked (consent, ad blocker), wrong property, or the container is still unpublished.

Fact table

Claim	Basket	From where
The current install path runs through GA4 Admin, Data streams, and the Google tag or GTM	Fact	Google Analytics Help on data streams and the Google tag.
Universal Analytics stopped processing new hits on 1 July 2023	Fact	Google Analytics Help: Universal Analytics has been replaced by Google Analytics 4.
Connected site tags were a legacy path to attach existing UA / gtag setups to GA4	Fact	Google Help “[UA→GA4] How gtag.js for UA maps to GA4 [Legacy]”.
GA4 event data retention is set under Admin, Data settings, and limits exploration lookbacks	Fact	Google Analytics Help on data retention.

Sources: Google Analytics Help: Data streams, Universal Analytics replaced by GA4, Legacy: gtag.js for UA maps to GA4.