Guide 185 · Conversions · GA4 + Tag Manager
Key event for video plays in GA4: video_start, video_complete, and which one to mark
Enhanced measurement sends video_start, video_progress, and video_complete for embedded YouTube videos, with the percent viewed on the progress events. Starting a video is cheap; finishing one is the signal. This guide marks video_complete for a product video, reads the progress marks, and works out the completion rate for a week.
After the steps, the video_complete key event appears under the Key events tab in Admin, and the standard reports show it within a day. The worked example below gives the count and the rate to expect.
Download the reference: the video_complete key-event reference (JSON) (707 bytes, MD5 19c5564c68175d913c5e6daa4118ad9d). It holds the event name, the counting method, the worked-example figures recomputed for this guide, and the checkpoints that prove the key event is recording. The figures in the file are the same figures shown on this page.
What you need
- Editor access or above at property level in GA4. Marking an event as a key event is a property setting, and the star in the Events table does not appear for a Viewer.
- Enhanced measurement enabled in the web data stream, so video events are collected. The events fire for embedded YouTube videos with the JavaScript API enabled.
- A video whose completion is the outcome. In this guide the video is the 3-minute product tour on the pricing page.
The trace
- Confirm the video events are collecting. Open Reports, then Engagement, then Events, and find the video_start, video_progress, and video_complete rows. If only video_start appears, visitors start the video and leave before the first progress mark.
- Check the video parameters in DebugView. Open Admin, then Data display, then DebugView, play the video, and watch video_start arrive with video_title and video_url, then video_progress at 10%, 25%, 50%, 75%, and 90%, then video_complete. The progress marks are what show where viewers leave.
- Choose video_complete, not video_start. Marking video_start makes every accidental play a key event. The product tour only matters when it is watched through, so the event to mark is video_complete.
- Mark video_complete as a key event. Open Admin, then Data display, then Events, and click the star on the video_complete row. A standard property can mark up to 30 events, and this is one of them.
- Read the completion count in the Events report. In the worked example the week shows 240 video_start events and 96 video_complete events. The completion rate is 96 / 240 = 40.00% of starts.
- Work out the session key event rate. The week shows 1,600 sessions and 88 sessions with a video_complete key event, which is 88 / 1,600 = 5.50%. The 96 completions came from 88 sessions, so 8 sessions watched the tour through more than once.
Dead ends
DEAD END — MARKING video_start AS THE OUTCOME. A start is a click on play, including the accidental ones. A video that starts 240 times and completes 96 times looks twice as successful as it is when the marked event is the start.
DEAD END — EXPECTING VIDEO EVENTS FOR A NATIVE PLAYER. Enhanced measurement video events fire for embedded YouTube videos with the JavaScript API enabled. A native HTML5 video player sends nothing on its own, and the events must be sent from Tag Manager instead.
DEAD END — READING video_progress AS COMPLETION. The progress marks stop at 90%. A viewer who reaches 90% and leaves never fires video_complete, and must not be counted as a completion.
End state
The video_complete event is the marked key event for the product tour. The week closes at 96 completions from 240 starts, a completion rate of 40.00%, and a session key event rate of 5.50%.
| Figure | Value |
|---|---|
| Sessions in the week | 1,600 |
| video_start events | 240 |
| video_complete key events | 96 |
| Completion rate, of starts | 40.00% |
| Sessions with a video_complete key event | 88 |
| Session key event rate | 5.50% |
The completion rate is 96 / 240 = 40.00% and the session rate is 88 / 1,600 = 5.50%, both recomputed in Python 3 and rounded to two places. The repeat count is 96 − 88 = 8. The figures are a worked example, not a real property.
Sources
- Analytics Help — [GA4] Recommended events — the recommended event names, including generate_lead, sign_up, and purchase
- Analytics Help — About key events — marking an event as a key event, the 30-event limit for a standard property, and 50 for Analytics 360
- Analytics Help — Monitor events in DebugView — watching events with their parameters in DebugView
Checked 11 November 2026. The click paths above are the ones in Google's help pages, read 11 November 2026. The video_start, video_progress, and video_complete events are enhanced measurement events for embedded YouTube videos, with progress at 10%, 25%, 50%, 75%, and 90%, and marking from Admin, then Data display, then Events, are as Google documents them. No step in this guide was run inside a live Analytics property, because Admin needs a Google sign-in and this site does not sign in as anyone. The figures on this page are a worked example recomputed in Python 3 with decimal arithmetic, not numbers from a real property. Google moves menu items without warning; if a path on this page no longer matches, the linked help page is the current map.