# Youtube Thumbnails > Use when designing or fixing a YouTube thumbnail, making variants for an A/B test, or working out which thumbnail style wins on a channel — including the trap where CTR looks fine but the test keeps selecting the duller image on watch-time share. NOT pairing the title with the thumbnail as one click-promise (that is `youtube-packaging`), NOT channel positioning or niche (that is `youtube-strategy`), NOT setting a thumbnail through the Data API (that is `youtube-api`). - Skill: `ericrisco/youtube-thumbnails` (Agent Skill, multi-file: 6 files) - Install (CLI): `npx skillmds@latest add ericrisco/youtube-thumbnails` - Raw SKILL.md: https://api.skillmd.com/api/skills/ericrisco/youtube-thumbnails/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Marketing & Growth - Author: ericrisco (https://skillmd.com/u/ericrisco) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/ericrisco/youtube-thumbnails --- # YouTube thumbnails Design thumbnails that survive the mobile feed, test them so the winner is a *lesson* and not a coin flip, and write every outcome back to the channel's wiki so the next thumbnail is evidence-led. A thumbnail you cannot learn from is half wasted. ## The loop This skill runs a closed loop, not a one-off design pass: 1. **Design** 2-3 candidate concepts that differ on exactly ONE testable axis. 2. **Test** them in YouTube Studio "Test & Compare". 3. **Log** the outcome to `02-DOCS/wiki/youtube/thumbnail-experiments.md`. 4. **Learn**: mine the log into `thumbnail-patterns.md` (what wins on THIS channel) and let that pick the next concept. The reason for the discipline: Test & Compare hands you a winner, never a reason. One varied axis per round is what turns a winner into a transferable rule. ## Hard constraints These are objective and machine-checkable. `scripts/verify.sh` enforces the image ones; the rest are your job. Source facts: socialrails.com / thumbnailtest.com specs, accessed 2026-06-02. | Constraint | Value | Why | |---|---|---| | Resolution | 1280x720 px | YouTube's recommended size; anything smaller upscales soft | | Aspect ratio | 16:9 | The only ratio that fills the player and feed cleanly | | Min width | 640 px | Below this YouTube may reject the upload | | File size | under 2 MB | Hard cap for standard video (10 MB only for podcast thumbnails) | | Format | JPG or PNG | Also accepts GIF/BMP, but ship JPG/PNG | | Legibility | reads at 320x180 | Most discovery is the mobile feed at ~that scale — the "squint test" | | Safe zone | clear bottom-right | The duration stamp overlays that corner — no critical text/face/logo there | The squint test: shrink the image to 320x180 (or step back two meters from the screen). If the subject and any text are not instantly readable, it fails — design for the feed, not for the editor canvas. See `references/composition-and-specs.md` for the contrast math and export workflow. ## Composition rules Each rule, one reason. Concrete beats abstract. - **One dominant focal point.** The eye must land in under a second; a thumbnail with two competing subjects reads as none at 320x180. - **A face with one strong emotion** when the video allows it. Faces with clear emotion lift CTR roughly 20-30%, and custom thumbnails run ~60-70% higher CTR than auto-generated frames. One emotion, not a neutral stare. - **Subject ~30% brighter or darker than its background.** Separation is what makes the subject pop in a scroll; a subject the same luminance as the bg vanishes. Add a subtle outline or glow if the background is busy. - **2-3 bold colors, complementary.** More than three and the image turns to mud at feed scale. Target a text/background contrast ratio of about 4.5:1 (a usability heuristic, not a YouTube rule). - **Kill motion blur and clutter.** Anything that softens or crowds the frame dies first when the image shrinks. ## Text rules - **3-4 words maximum, maximum weight.** Heavy bold sans, large enough to read at 320x180. If it needs a second line of small type, cut it. - **Never in the bottom-right.** That is the duration-stamp safe zone. - **The thumbnail text must NOT just repeat the title.** They are two surfaces of one promise, so make them add up instead of echo. Bad -> Good (text that wastes the surface): ```text Bad title: "I built a PC in 24 hours" thumb text: "BUILT A PC IN 24H" Good title: "I built a PC in 24 hours" thumb text: "$200 BUDGET?!" ``` The Bad version spends both surfaces on the same words. The Good version lets the thumbnail carry the stakes the title leaves implicit. The *full* title<->thumbnail promise pairing — which surface owns which half of the hook — belongs to [youtube-packaging](../youtube-packaging/SKILL.md). Here, just don't duplicate. ## Variant design for the A/B test This is where the flow branches, so decide deliberately. **Vary exactly ONE axis per variant set.** Change face vs object AND text AND color at once and a winning variant teaches you nothing — you cannot attribute the lift. Pick one axis from the menu and hold everything else constant. | Axis | Variant A | Variant B | What a win tells you | |---|---|---|---| | Subject | human face | the object/result | does your audience click people or things | | Expression | shock | calm/confident | which emotion this niche rewards | | Text | text present | no text | whether words help or clutter here | | Color | warm dominant | cool dominant | the channel's palette pull | | Layout | subject left | subject right | reading-order fit | | Zoom | tight crop | wide context | intimacy vs setting | Two variants is enough to isolate one axis cleanly; use the third slot only when a third level of the SAME axis is genuinely informative. ## Test & Compare procedure YouTube's native A/B tool (broad rollout 2025). In Studio: open the video -> Thumbnail -> "Test & Compare" -> add variants. - **Up to 3 thumbnails** (and/or titles) per video. - **Winner is chosen by watch-time share, NOT raw CTR.** This is the trap that breaks intuition: a punchy over-promising thumbnail can win the click and still *lose* the test because the viewers it lured bounce, dragging watch time down. - **Runs up to ~2 weeks**, then YouTube auto-promotes the winner. - Let it reach significance — don't call it after two days of noise. The over-promise trap is the seam to [youtube-packaging](../youtube-packaging/SKILL.md): if your tests keep crowning the "boring" variant, the flashy one is writing a check the video doesn't cash. That is a promise problem, not an image problem. ## The feedback loop (wiki) Every test result goes to the channel wiki. Exact path: `02-DOCS/wiki/youtube/`. `02-DOCS/wiki/` is an **OKF v0.1** bundle: both files below carry file-level frontmatter with a non-empty `type` (`thumbnail-experiment`) plus the OKF surface (`title`, `description`, `tags`, `timestamp`) shared with the api/strategy/packaging siblings, and cross-references use standard markdown links, never `[[wikilinks]]`. **Log file** — `thumbnail-experiments.md`, frontmatter at the top then one row per test (append-only, ISO 8601 dates, past rows immutable): ```text | date | video | variants | axis tested | winner | CTR | watch-time share | note | ``` **Derived file** — `thumbnail-patterns.md`, frontmatter at the top then a running table of what wins on THIS channel (e.g. "faces beat objects 4/5 tests", "no-text wins on tutorials"). You update this after each logged test. **Next-concept rule:** the next thumbnail keeps the winning level of every axis already settled by the log, and tests the next unsettled axis. You only re-test a settled axis when the channel's content or audience visibly shifts. **Caveat:** on a small channel a single test is noise. Treat a pattern as real only after it holds across ~3+ tests or a clear, repeated margin. Full schema, filled example rows, and the pattern-mining heuristic live in `references/experiment-log-format.md`. ## Anti-patterns | Anti-pattern | Why it fails | Do instead | |---|---|---| | Tiny or thin text | Illegible at 320x180 feed scale | 3-4 words, heavy bold, squint-tested | | 5+ colors | Muddies into noise when shrunk | 2-3 complementary bold colors | | Clipart / stock faces | No emotion, no trust, reads as spam | Real face, one strong emotion | | Thumb text == title text | Wastes both surfaces of the promise | Thumb adds the stake the title omits | | Varying 3 axes per test | Winner is uninterpretable | One axis per variant set | | Trusting one test on a small channel | That's noise, not signal | Wait for ~3+ tests / repeated margin | | Designing in the full editor only | Looks great at 1280, dies in the feed | Check the 320x180 squint view | | Subject/logo in bottom-right | Duration stamp covers it | Keep that corner clear | | Chasing CTR while watch time tanks | Test & Compare scores watch-time share | Fix the over-promise (see youtube-packaging) | ## Pre-publish checklist - [ ] Exactly 1280x720, 16:9, under 2MB, JPG or PNG (run `scripts/verify.sh`) - [ ] Passes the 320x180 squint test - [ ] Bottom-right corner clear of text/face/logo - [ ] Single dominant focal point; subject ~30% contrast vs background - [ ] 3-4 words max, heavy weight; text not duplicating the title - [ ] 2-3 colors only - [ ] Variant set differs on exactly ONE named axis - [ ] Test & Compare configured (<=3 variants, watch-time-share, ~2-week window) - [ ] Log row staged for `02-DOCS/wiki/youtube/thumbnail-experiments.md` ## See also - [youtube-packaging](../youtube-packaging/SKILL.md) — the title<->thumbnail promise pair and hook framing. - [youtube-strategy](../youtube-strategy/SKILL.md) — channel positioning, niche, cadence. - [ab-testing](../ab-testing/SKILL.md) — rigorous experiment design on non-YouTube surfaces. - [design](../design/SKILL.md) — general visual systems and composition theory.