By name: thumbnail-ab-tester description: Generates multiple thumbnail concepts for the same clip and ranks them by hook strength using contrast, face presence, text legibility, and emotional cue heuristics. Trigger when user wants thumbnail options, A/B test thumbnails, or improve CTR on Reels/Shorts/YT.
Thumbnail A/B Tester
Generate 3-5 thumbnail concepts, score them, ship the winner.
When to use
- User has a video and wants 3+ thumbnail variants.
- User wants critique on an existing thumbnail.
- User wants to know which still frame from a clip is strongest.
Variant generation strategy
For one clip, produce variants across these axes:
| Axis | Option A | Option B | Option C |
|---|---|---|---|
| Frame | Hook moment (start) | Climax (mid) | Payoff (end) |
| Text | One word | Short phrase | None (visual only) |
| Face | Tight crop (eyes visible) | Medium shot | Object only |
| Contrast | Dark bg + bright subject | Inverted | High saturation |
Pick one option per axis → 3-5 thumbnails total. Don't generate 30 — too much noise.
Scoring rubric (0-10 each, sum / 40)
| Factor | What to check |
|---|---|
| Hook clarity | Can a viewer read the story in < 1 sec? |
| Face / emotion | If a face: is the emotion strong & specific? |
| Text legibility | Readable at 320px wide (IG feed size)? |
| Contrast | Subject pops from background? |
Heuristics (the boring stuff that matters)
- Faces with visible eyes outperform face-from-behind ~2:1 on IG.
- Bright single-colour backgrounds (yellow, red) beat busy stills.
- Text on thumbnail: ≤ 4 words. Beyond that, no one reads.
- Avoid feed-camouflage: if your thumbnail looks like 5 others on the explore grid, it loses.
When to NOT use a thumbnail
- IG Reels cover image is shown on grid only, not feed. Optimise for grid coherence + first-frame hook in the video, not feed clicks.
- YT Shorts: thumbnail = first frame by default. Either accept it or pin a custom cover.
Output
Variant A — score 32/40
Frame: t=2.4s (climax)
Text: "₹4,300 in 14 min"
Notes: high contrast, specific number, face in lower third
Strongest factor: hook clarity
Variant B — score 28/40
...
Winner: A
Why: specific number + face emotion drives the highest CTR pattern.
What NOT to do
- Don't fabricate emotions / numbers in thumbnails. Clickbait that doesn't deliver tanks your reach next post.
- Don't use ©'d game promotional art as a thumbnail.