What is GA4 (Google Analytics 4)?
Also known as: GA4, Google Analytics 4
What is GA4?
Google Analytics 4 is Google's current web and app analytics platform. It replaced Universal Analytics on July 1, 2023, when Google sunset UA's data collection. Every new property since October 2020 has been GA4.
GA4 is built on a single event model. A pageview is an event. A click is an event. A purchase is an event. Each event carries parameters, key-value pairs that describe what happened. The model unifies web and app data in one property.
The platform is free for standard use. The paid tier, Analytics 360, lifts data caps and adds enterprise SLAs.
GA4 vs Universal Analytics
GA4 is not a UA upgrade. It is a different product with a different data model. Per the Google Analytics help center, every UA report logic was rewritten for GA4.
The differences that trip teams up most often:
| Area | Universal Analytics | GA4 |
|---|---|---|
| Data model | Sessions and pageviews | Events with parameters |
| Bounce rate | Single-page visits | Inverse of engagement rate |
| Conversion counting | One per session | One per event by default |
| Attribution default | Last non-direct click | Data-driven |
| BigQuery export | 360 only ($50k+/yr) | Free on every property |
| Data retention | 26 months max | 14 months max (standard) |
| Mobile + web | Separate properties | One property, multiple streams |
The free BigQuery export is the single biggest win. UA locked raw data behind the 360 paywall. GA4 ships it standard. Teams that never touched warehousing now have row-level event data to query.
Core GA4 concepts
Four primitives run the platform. Get these right and the rest follows.
Events
Everything is an event. GA4 splits events into four types:
- Automatically collected.
page_view,session_start,first_visit. Ship by default. - Enhanced measurement.
scroll,click(outbound),video_start,file_download. Toggled in the data stream. - Recommended.
purchase,sign_up,generate_lead,add_to_cart. Predefined names with predefined parameters. - Custom. Anything you define yourself.
Use recommended events when one fits. The reports built into GA4 expect those exact names.
Parameters
Each event carries up to 25 parameters. Parameters answer the "what" of the event. A purchase event might carry value, currency, transaction_id, items. Without parameters, an event is a noun with no detail.
Conversions
Any event marked as a conversion counts toward conversion reports. Mark up to 30 conversions per property. As of 2024, GA4 renamed "conversions" to "key events" inside the UI, but the function is identical.
Audiences
Audiences are saved segments built from events, parameters, and user properties. They sync to Google Ads for retargeting and to BigQuery for analysis. Build audiences before you need them. Membership is forward-looking only.
How to set up GA4
Setup runs in four steps. Budget two hours for a basic install. A full ecommerce instrumentation runs one to two weeks.
1. Create the property
In the Admin panel, create a new property. Pick a time zone and currency. These cannot be changed later without losing data continuity.
2. Add data streams
A data stream is one source of data, a website or an app. Add a web stream for your domain. The stream gives you a Measurement ID (G-XXXXXXXX). Drop the gtag snippet on every page, or fire it through Google Tag Manager.
3. Configure events
Turn on enhanced measurement. Add recommended events for your business model. Per the Google Analytics help center, GTM is the supported path for custom events. Test every event in DebugView before publishing.
4. Mark conversions
In Admin > Events, flip the "Mark as key event" toggle on the events that matter. Common picks: purchase, generate_lead, sign_up. Link the GA4 property to Google Ads to push conversions into conversion tracking for bidding.
GA4 attribution models
GA4 ships six attribution models. The default is data-driven. The choice affects how credit is split across touchpoints in a multi-touch attribution report.
| Model | What it does |
|---|---|
| Data-driven (default) | ML-assigned credit based on actual conversion patterns |
| Cross-channel last click | Last non-direct touch gets 100 percent |
| Cross-channel first click | First touch gets 100 percent |
| Cross-channel linear | Equal split across all touches |
| Cross-channel position-based | 40 percent first, 40 percent last, 20 percent middle |
| Paid and organic last click | Last paid or organic touch wins, direct excluded |
The conversion lookback window defaults to 30 days for acquisition, 90 days for all other conversions. Adjust in Admin > Attribution settings to match your sales cycle. A SaaS with a 6-month sales cycle reports nothing useful at 90 days.
Common GA4 issues
Three problems show up in almost every audit. Fix these first.
Cookie banners blocking the tag. Consent Mode v2 has been mandatory in the EEA since March 2024. If the banner blocks gtag before consent, GA4 sees a fraction of traffic. Wire Consent Mode signals or accept the data gap.
Cross-domain measurement broken. Default GA4 treats cart.example.com and www.example.com as separate sites. Add both to the cross-domain list in the data stream settings, or every checkout looks like a referral.
Internal traffic counted. Office IPs, staging environments, and QA bots inflate sessions. Add IP filters and a traffic_type=internal parameter to test events. Check the realtime report from a fresh device to confirm.
A fourth issue, sampling, hits sites above 10 million events per month. The fix is BigQuery export, which is unsampled by default.
Real-world example: a well-instrumented funnel
A B2B SaaS team runs paid search and content marketing. Their GA4 funnel tracks five steps from first visit to closed deal.
| Step | Event | Conversion? |
|---|---|---|
| 1. First visit | first_visit | No |
| 2. Pricing page view | page_view (path = /pricing) | No |
| 3. Demo request | generate_lead | Yes |
| 4. Trial start | sign_up (method = trial) | Yes |
| 5. Paid plan | purchase (value = MRR x 12) | Yes |
Each event carries utm_source, utm_campaign, and an internal account_id. The team exports raw events to BigQuery. They join GA4 events to Salesforce opportunity data on account_id.
Result. A blended view of paid spend, content engagement, and pipeline. The team sees that content traffic converts to demo at 0.8 percent and to closed deal at 0.04 percent. Paid search converts to demo at 2.4 percent and to closed deal at 0.18 percent. Same property. Two different acquisition stories. The instrumentation made the comparison possible.
The tracking is the product. A clean GA4 property is the difference between guessing what worked and knowing. Pair it with bounce rate signals on landing pages and a clear pixel setup on paid channels, and most reporting questions answer themselves.
Related terms
Frequently asked questions
Is GA4 free?
Yes. The standard GA4 property is free for any site or app. Google Analytics 360, the enterprise tier, costs around $50,000 per year and lifts data limits, sampling thresholds, and SLAs. Per the Google Analytics help center, the free tier is enough for most sites under 10 million events per month.
What happened to bounce rate in GA4?
It came back in 2022 but with a new definition. GA4 bounce rate is the inverse of engagement rate. A session is engaged if it lasts 10 seconds, fires a conversion, or has 2+ pageviews. Anything else is a bounce. The old Universal Analytics bounce rate (single-page visit) is gone.
Why is my GA4 data different from Universal Analytics?
Different model. UA counted sessions and pageviews. GA4 counts events. Conversions are deduplicated differently. Attribution defaults to data-driven instead of last-click. Expect 10 to 30 percent variance on the same site. Compare trends over time, not absolute numbers between the two systems.
Do I need BigQuery to use GA4 properly?
No, but it helps. The free GA4 to BigQuery export gives you raw event-level data with no sampling. Without it, the GA4 UI samples reports above 10 million events. Most teams above 100k monthly users turn the export on within the first month.
How do I track conversions in GA4?
Fire an event, then mark it as a conversion in Admin > Events. GA4 ships with automatic events (page_view, scroll, click) and recommended events (purchase, sign_up, generate_lead). Custom events use gtag, GTM, or the Measurement Protocol. Per Simo Ahava's blog, GTM remains the cleanest way to manage events at scale.