Watch time
Also known as: retention
Watch time is the cumulative duration viewers spend watching a video, expressed either as average watch duration per view or as percentage retention curve across the clip's length. For short-form algorithms (TikTok, Reels, Shorts), watch time is the dominant ranking signal — clips with high retention get distributed to more feeds regardless of like/comment counts.
Short-form algorithms reward two retention metrics. (1) Completion rate — what percentage of viewers watched to the end. (2) Replay rate — what percentage looped the clip. Both signal that the clip held attention beyond the standard scroll-past. A 30-second clip with 80% completion outperforms a 60-second clip with 60% completion even though raw watch-seconds-per-view favor the longer clip.
The retention curve matters as much as the average. A clip that loses 50% of viewers in the first 3 seconds and holds the rest to the end performs worse than a clip that loses 5% in the first 3 seconds and gradually decays. The first 3 seconds get weighted disproportionately. This is why the viral-hook is the highest-leverage edit decision.
Practical implication: clip length should match content density, not creator preference. A 25-second clip that lands hard outperforms a 70-second clip that includes the same payoff plus filler. Clipzing.com's viral-scorer favors candidates in the 30-50 second range partly because that's where retention curves stay highest in 2026.
Related terms
Viral hook
A viral hook is the first 1–3 seconds of a short-form video clip — the line, image, or question designed to stop the thumb-scroll and earn the next 5 seconds of attention. In 2026, hooks that lead with a specific number, a stand-alone declarative sentence, or a contradiction outperform vague openers by an order of magnitude in retention.
Viral score
A viral score is an AI-generated numerical estimate of how likely a candidate video clip is to perform on short-form platforms. AI clip generators compute viral scores by analyzing multiple signals — speech cadence, hook strength, length, visual cuts, emotional peaks — and ranking candidate clips so creators publish the highest-scoring ones first.
Short-form video
Short-form video is the category of video content typically 15 to 90 seconds long, formatted in 9:16 vertical aspect ratio, designed for thumb-scrollable mobile feeds. The dominant short-form platforms in 2026 are TikTok, Instagram Reels, YouTube Shorts, and Snapchat Spotlight. Long-form video (3+ minutes) lives on YouTube and traditional video platforms.