video_thumbnails v1.0.0

name: "video_thumbnails" description: "Design video thumbnails that win the click: composition, short-text rules, contrast, CTR basics, and testing (YouTube Test & Compare). Triggers when someone needs a thumbnail designed, critiqued, or iterated — or asks how to raise video click-through rate."

Video Thumbnails

Purpose

Turn a video's promise into a thumbnail that earns the click against a feed of competitors. Used two ways: design (produce concepts, mockups, and a final spec for the image generator) and critique (score an existing thumbnail and prescribe fixes). Facts below are from YouTube Help, verified 2026-09-20; full citations live in references/design-playbook.md.

Workflow

1. Lock the promise first. One line: what the viewer gets from this video. Write the video title before touching the thumbnail — the thumbnail's job is to create tension with the title, not repeat it. Never put title words on the thumbnail.
2. Generate 3 concepts, each with ONE hook (face + strong emotion, before/after, big number, versus, curiosity gap — the eye sees the outcome but not the cause, or a pattern interrupt that breaks the niche's visual convention). One hook per thumbnail; stacking hooks dilutes them.
3. Compose each concept: one dominant focal subject (rule of thirds), one short headline block (3–5 words, bold sans-serif, high stroke), a background that contrasts the subject, and negative space so it breathes. Keep it simple — complexity loses to clarity at feed size.
4. Validate mechanically. For each concept run bin/thumb_mockup.py --spec spec.json --out mock.png (renders a labeled layout mockup plus a 160px-wide squint preview — the size text must read at on mobile) and bin/text_contrast.py --fg FFFFFF --bg 101418 for every text/background pair (pass bar: contrast ratio ≥ 3.0 for large thumbnail text, aim ≥ 4.5). If the squint preview is unreadable or the contrast fails, fix the concept — never ship it.
5. Pick a winner by critique, then write the final spec for the image tool: subject description + emotion/pose, background, exact headline text, color palette (hex), and what must NOT appear (no title words, no logos clutter, no misleading visuals).
6. Export to platform spec: 1280×720, 16:9, JPG or PNG, ≤ 2 MB (safe on every upload path). YouTube Help also lists 3840×2160 as recommended with a higher desktop limit, but 1280×720 renders everywhere and never gets rejected.
7. Test, don't guess. If YouTube Studio's Test and Compare is available: upload up to 3 meaningfully different variants (not font-size tweaks), let it run to completion (~2 weeks max), and accept that the winner is chosen by watch-time share, not CTR. Otherwise: swap thumbnails manually only after the video stabilizes (7–14 days), then compare impressions CTR on Home/Suggested in comparable 24–48h windows.
8. Read the numbers honestly. Per YouTube Help, half of all channels/videos sit at 2–10% impressions CTR — compare a video against similar videos on the same channel, not against a universal benchmark. High CTR + falling average view duration = clickbait signal; that thumbnail is hurting the channel.

Output Contract

• Design task: 3 concept cards (hook, layout, headline text, palette) + mockup PNGs + squint previews + a chosen final with a copy-paste image-generation prompt + export spec + test plan (Test & Compare variants or manual-swap schedule).
• Critique task: scorecard on focal clarity / text legibility at feed size / color contrast / title synergy / clickbait risk, each with a concrete fix ("headline fails 160px test → cut to 3 words and move to lower third").

Operating Rules

1. Honesty beats clickbait. The thumbnail must depict what the video actually delivers. Misleading thumbnails are prohibited by YouTube's deceptive-practices policy and YouTube Help explicitly says chasing CTR with clickbait lowers recommendations. Never propose one.
2. Never repeat the title on the thumbnail. Wasted pixels; the packaging unit is thumbnail + title together.
3. No concept ships without a squint preview and a contrast check. The tools in bin/ are the gate, not the taste.
4. Facts about the platform are verified, not remembered. Specs, CTR ranges, and Test & Compare mechanics in this skill were verified against YouTube Help on 2026-09-20 — see references/design-playbook.md. If the platform changes, re-verify before asserting.