Conversion events (key events)
A conversion event is an ordinary event you have marked as important — a purchase, a signup, a qualified lead. GA4 now calls these 'key events'. Nothing about the event changes; marking it tells the platform to count it as a conversion and build conversion reports around it. The decisions that matter are which events to mark, and whether to count once per session or every time.
What this means
A conversion is an action you decide counts as success. In GA4 you mark an existing event as a 'key event' (formerly 'conversion'), and the platform then treats it as a goal: conversion reports, conversion rate, and attribution all key off it. The event itself — purchase, sign_up, generate_lead — is unchanged; the marking is what makes it a conversion.
Which events, and how to count
Mark only events that represent real value — too many 'conversions' and the term means nothing. Then choose a counting method: count once per session (good for a goal a person should achieve once, like a signup) or every time (good for purchases, where each one is real value). Picking the wrong method is the most common reason conversion numbers look implausible.
- A conversion is a marked event, not a new event type
- GA4 calls them 'key events'
- Count once-per-session or every-time deliberately
How it appears in analytics and logs
A conversion count that exceeds the number of users for a once-per-customer goal means the counting method (every-time vs once) is wrong, not that conversions are booming.
Diagnostic use case
Mark the handful of events that represent business success as conversions (key events), so conversion reporting reflects real goals rather than every action.
What WebmasterID can help detect
WebmasterID lets you designate first-party events as goals and reports on them without third-party cookies, so conversion measurement stays first-party and privacy-safe.
Common mistakes
- Marking too many events so 'conversion' loses meaning.
- Using every-time counting for a once-per-customer goal.
- Forgetting that the no-PII rule still applies to the event.
Privacy and accuracy notes
Marking an event as a conversion changes how it is counted, not what it stores — the same no-PII rules apply to its parameters. This is educational, not legal advice.
Related pages
- Conversion rate: definition and denominators
Conversion rate is the share of some base that converted. The trap is the denominator: conversions per session, per user, and per unique visitor give different numbers and mean different things. Without stating the base, a conversion rate is ambiguous — and comparing rates with different bases is meaningless.
- The purchase event and e-commerce
The purchase event records a completed transaction and anchors all e-commerce reporting: revenue, items, and conversion value. It carries a transaction id, a value and currency, and an items array describing what was bought. The discipline is to record the order, not the customer — product and revenue data belong in the event, personal identity does not.
- The form_submit event
A form_submit event records that a visitor submitted a form — a signup, contact, or checkout form. It is one of the highest-value events because it usually maps to an intent or conversion. The hard rule is that the submitted field values (name, email, message) must never enter analytics: you record that a form was sent and which one, not what was typed.
- Attribution analytics
Attribute conversions to their sources first-party.
Sources and verification notes
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.