What Is a Virality Score? How AI Clip Tools Rate Your Clips (and What They Can't See)

Most AI clipping tools now put a number on every clip: 86/100, 9.2/10, "score 94". It is meant to answer one question: which of these twenty clips should I post first? This page explains what that number measures, how Katto computes its own score rule by rule, and what no virality score can see.

Disclosure: I build Katto. The scoring rules below are read from Katto's code as of November 10, 2026.

What a virality score is (and isn't)

A virality score is a ranking signal, not a view forecast. The tool cuts a long video into candidate moments, then rates each one on features that tend to keep people watching: a strong opening, a complete thought, dense speech, emotional words, numbers. The score lets you sort clips. It does not know your audience, your thumbnail, your posting time or the algorithm's mood that day.

Here is how the tools we track present it, checked on their own pages:

• OpusClip: a virality score built on four dimensions, Hook, Flow, Value and Trend.
• Katto: the same four dimensions, 0 to 100, with a written explanation per clip.
• Vizard: a viral score from 0 to 10 with a short reason, and clips sorted by it.
• Riverside: Magic Clips ranked with a score from 70 to 99.
• Submagic and Klap: a virality score on generated clips.

How Katto scores a clip, rule by rule

Katto's score is the sum of four parts. The exact rules matter because they tell you what to change if a clip scores low.

Hook (up to 30 points): the first 3 seconds

• A question word among the first three words: +10.
• Impact words in the first 3 seconds (words like "never", "always", "secret"): +5 each, up to +10.
• An opening that doesn't start with filler ("so", "and", "but", "because"): +5.
• A number or percentage in the opening: +5.
• An outro in the opening ("thanks for watching", "subscribe"): -15. A goodbye is a dead hook.

Flow (up to 30 points): does it hold together?

• Speech density, measured by voice detection: up to 12. Long silences lose points.
• Scene stability: 12 points with at most one camera cut, 8.5 with two or three, 3.5 with more. Jumpy footage reads as messy in a short.
• Audio energy: up to 6 for a sustained, steady level.

Value (up to 25 points): is it worth watching on its own?

• Impact words and numbers across the whole clip: up to 15.
• A clean start (not "and", "so", "because") and a clean end (a finished sentence): 5 points each.
• Self-promotion dense enough to read as an ad: up to -15.

Trend (up to 15 points): shareable patterns

• Contains a question: +4. Contains a number or statistic: +4.
• Emotional words ("crazy", "nobody", "worst", "incredible"): +4.
• Audio energy peaks, a sign of excitement: up to +3.
• Heavy self-promotion: -8.

Two adjustments on top

• Intros are down-weighted. The first minutes of a long video are often a cold open, a sponsor read or "welcome to the show". They sound energetic but rarely make the best clip.
• Your topic adds points. If you tell Katto what you are looking for ("moments about pricing", "the funny parts"), clips that match get up to +30. That is why a score can go above 100.

Clips with little or no speech (gameplay, sports, trailers) are scored on visual signals instead, since there are no words to read.

A real example: the highest score isn't always the post

We ran NASA's Artemis II post-splashdown news conference through Katto. The top clip scored 100.4: dense, on-topic, full of numbers about how NASA plans to fly to the Moon more often. But it opens mid-sentence, on a technical point. The clip we actually posted as a Short scored 86: a NASA leader remembering seeing Star Wars with his father, and the crew that just flew farther than any humans before. Same video, lower score, better first two seconds for a feed.

That is the right way to use a virality score: shortlist with it, then watch the top five and judge the opening yourself.

What no virality score can see

• Your audience. A niche technical clip can outperform a "hooky" one with the right followers.
• The visual opening. Rules based on words don't see a cutaway to the audience or a blurry first frame.
• Timing and trends outside the video: news, memes, what the platform is pushing this week.
• Packaging: title, caption, thumbnail and the first line of text.

How to raise a clip's score (and its real chances)

1. Trim to the first strong sentence. Start on the question or the bold claim, not on "so, yeah".
2. End on a finished thought. Cut after the punchline, not mid-sentence.
3. Cut the self-promo. "Link in bio" inside the clip costs points and attention.
4. Add a text hook over the first seconds when the spoken opening is weak.
5. Tell the tool what you want. A topic hint pulls the right moments up the list.

FAQ

What is a good virality score?

Treat it as a ranking within one video rather than an absolute grade. On Katto, a low score usually means the clip starts or ends mid-sentence, has long silences or reads like an ad; the four sub-scores tell you which.

Does a high virality score guarantee views?

No. It predicts which clips are structurally strong. Views depend on your audience, packaging and timing, which no clipping tool sees.

Why can a Katto score be above 100?

The base score tops out at 100 (30 + 30 + 25 + 15). When you give Katto a topic, clips matching it get up to 30 bonus points so they rank first.

Is Katto's score the same as OpusClip's?

Both use Hook, Flow, Value and Trend, but the rules and weights are each tool's own, so the numbers are not comparable across tools. Katto publishes its rules here; compare clips within the same tool.