Video completion rate
Video completion rate is the percentage of video plays that reached the end. It is usually built from quartile progress events — playback milestones at 25%, 50%, 75%, and 100% — so completion rate is the 100% milestone divided by starts. It signals whether content holds attention, but auto-play, muting, and background tabs can inflate completions that no one actually watched.
What this means
Video completion rate = videos played to 100% ÷ videos started, as a percentage. In ad and media measurement it is typically derived from quartile events the player fires as playback crosses 25%, 50%, 75%, and 100% — so the same instrumentation yields a drop-off curve and the final completion figure.
Quartiles and what completion hides
Tracking quartiles is more informative than the single completion number: the gap between the 25% and 50% milestones, for instance, shows where interest collapses. Completion rate alone can mislead because a played-to-end count does not require attention — an auto-playing, muted video in a background tab can reach 100% with no human watching. Read completion alongside whether playback was user-initiated, audible, and in the foreground.
- Built from 25/50/75/100% quartile progress events
- Completion = 100% milestone ÷ starts
- Auto-play, muted, and background plays inflate completion
How it appears in analytics and logs
A completion rate tells you how often a started video was watched to the end. A high rate with auto-play or muted playback can overstate real attention, so read the quartile curve, not just the final number.
Diagnostic use case
Use video completion rate, read against the quartile drop-off curve, to find where viewers abandon and whether the ending is reached.
What WebmasterID can help detect
WebmasterID can record first-party video progress events, so quartile completion is measured on your own pages without third-party cookies or fingerprinting.
Common mistakes
- Reading completion rate without the quartile drop-off curve.
- Counting muted background-tab completions as real watches.
- Comparing completion across user-initiated and auto-play contexts.
Privacy and accuracy notes
Completion rate is built from aggregate playback-progress events, not personal identity. It needs no personal identifiers to compute.
Related pages
- Video view rate
Video view rate is the share of video impressions that counted as a view, but the metric hinges on each platform's definition of 'a view'. A skippable in-stream (TrueView) view counts after 30 seconds or completion (or an interaction); auto-play, muted, and click-to-play videos each trigger views under different rules. Because the threshold varies, view rates are only comparable within one platform's definition.
- Video play rate
Video play rate is the share of opportunities that resulted in a video play — typically plays divided by the number of times the video loaded or the page was viewed. It measures how often people start a video, but the metric is dominated by the denominator choice and by whether playback is auto or user-initiated, so play rate is meaningful only when those are held fixed.
- Scroll depth as an engagement signal
Scroll depth tracks how far down a page a visitor reaches, usually as percentage thresholds (25/50/75/90%) or a single 'reached bottom' event. GA4's enhanced measurement fires a scroll event at 90% vertical depth. It is a useful proxy for whether content was seen, but scrolling is not reading, and dynamic or short pages can trigger or suppress the event in misleading ways.
- Event Explorer
Inspect first-party video quartile events.
Sources and verification notes
- Google Analytics Help — [GA4] Video engagement events (video_progress)
- IAB — Digital Video Ad Serving Template (VAST) quartile trackingVAST defines the firstQuartile/midpoint/thirdQuartile/complete events.
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.