The short answer
GA4 records everything as an event. A session is a visit, which ends after 30 minutes of inactivity by default. An engaged session lasts over 10 seconds, includes a key event, or has two or more page views. A key event is an action important to your business. Open Acquisition, Engagement, Pages, and your key events first.
The model: everything is an event
Older versions of Google Analytics were built around page views and sessions. GA4 is built around events. An event is a single recorded action: a page loading, a scroll, a click on an outside link, a form submission, a file download. Every number you see is a count or grouping of events.
Some events are collected automatically once the Google tag is on your site. Others come from "enhanced measurement", a setting that records page views, scrolls to roughly 90 percent of page depth, clicks on links leading away from your site, file downloads and form interactions. Anything beyond that, such as a phone tap, needs to be set up. See track calls and forms.
Key terms, defined
Because user and session counts are estimates, treat small differences as noise. A difference of 2 percent between two reports is not a finding.
| Term | What it means in GA4 | Watch out for |
|---|---|---|
| Session | A period of time during which a user interacts with your website or app. By default it times out after 30 minutes of inactivity. | One person can have many sessions. |
| Engaged session | A session that lasts longer than 10 seconds, includes a key event, or has at least two page or screen views. | The 10 second timer can be adjusted in settings, so check yours. |
| Engagement rate | The percentage of sessions that were engaged sessions. | It replaces most of what bounce rate used to say, and is not the same thing. |
| Users | People, approximated by devices and browsers, who interact with the site. Session and user metrics are calculated through an estimation. | The same person on phone and laptop can appear as two users. |
| Event | A recorded interaction, such as page_view or form_submit. | Events are only as good as the tracking behind them. |
| Key event | An event that measures an action particularly important to the success of your business. | This is the new name for what GA4 used to call a conversion. You choose which events are key events. |
| Channel | A group of traffic sources, such as Organic Search, Paid Search, Direct, Referral or Email. | Channel assignment follows Google rules, not your marketing plan. |
Channels and the "Direct" bucket
GA4 sorts each session into a default channel group using the source and medium of the visit. Organic Search is unpaid Google or Bing results. Paid Search is ads. Referral is a link from another website. Email, Organic Social and Direct are what they sound like. Visits from AI assistants such as ChatGPT or Gemini can appear in their own channel on newer properties, or fall under referral or direct on older setups, depending on configuration.
"Direct" is the most misunderstood label. It does not only mean people typing your address. It is also where visits land when GA4 cannot see where they came from: some app links, some email apps, some private or secure sources. A growing Direct share is often a sign of lost source data, not a surge of loyal customers.
Attribution in one paragraph
Attribution is the rule for which channel gets credit for a key event when a person touched several channels before converting. GA4 offers data-driven attribution, which distributes credit using machine learning on your account's data, and last-click-style models, which give full credit to the last channel clicked. GA4 reports exclude direct visits from credit unless the whole path was direct. The practical lesson: a channel that starts journeys, such as search, may look weaker than one that finishes them, such as an email or a brand search. Judge channels in context, not alone. More in why numbers differ.
Data retention and thresholds
GA4 does not keep detailed data forever. For standard properties, the event data retention setting is either 2 months or 14 months, and it applies to the detailed, user-level data used in explorations. The standard summary reports are not affected. Age, gender and interest data always use a two-month window. If you only compare against last year in explorations, make sure retention is set to 14 months, which is a setting an administrator of the property can change.
GA4 can also apply data thresholds. These are system-defined limits that withhold data in reports when low counts could let someone identify individual users, especially with demographic information. If you see a notice that thresholding has been applied, the numbers are not wrong, but some rows are hidden. A longer date range often helps, because larger counts clear the threshold.
Data retention is not retroactive. Raising it from 2 to 14 months does not bring back data you already lost.
The first four reports to open
- 1Reports snapshot (the home page of Reports): a quick view of users, events, key events and where people come from. Check the date range at the top first, because it resets.
- 2Acquisition, then Traffic acquisition: how many sessions came from each channel and how many key events each produced. This answers "where do my results come from?"
- 3Engagement, then Pages and screens: which pages people view and how long they engage. Use it to see which pages attract attention and whether they lead to action.
- 4Key events (under Engagement, or the Events list): how many times each of your important actions happened. If this is empty or low for something you know happens, tracking needs checking.
Four habits that prevent misreading
- Always set and read the date range, and compare with the previous period or year.
- Look at engaged sessions and key events, not just sessions.
- Use channel reports to see where results come from, not to rank who is winning.
- Remember cookie consent and bots affect counts. See why numbers differ.
When to ask us
Ask us if a key event is not firing, if your channels look wrong (for example nearly everything in Direct), if you cannot see the reports above, or if retention seems too short to compare with last year. Use the support form and choose Report or analytics question. You will not need to give anyone a password: tell us what you can and cannot see and we will find another way, such as inviting you with the right access from within GA4.
- The report name and the date range, with a screenshot.
- What you expected, for example a form you know was sent on a given day.
- Whether you can open Admin in GA4. Do not send login details.
- Files as Google Drive, Dropbox or Loom links.
