Agent skill

youtube-thumbnail-design

YouTube thumbnail design with specific dimensions, contrast rules, and mobile preview optimization. Covers safe zones, text placement, face expression psychology, and A/B testing. Use for: YouTube thumbnails, video cover images, click-through optimization. Triggers: youtube thumbnail, thumbnail design, video thumbnail, click through rate, ctr optimization, youtube cover, video cover image, thumbnail maker, thumbnail tips, youtube design, video preview image

View SKILL.md on GitHub Repository
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Install this agent skill to your Project

npx add-skill https://github.com/inference-sh/skills/tree/main/guides/design/youtube-thumbnail-design

SKILL.md

YouTube Thumbnail Design

Create high-CTR YouTube thumbnails with AI image generation via inference.sh CLI.

Quick Start

Requires inference.sh CLI (infsh). Install instructions

bash
infsh login

# Generate a thumbnail
infsh app run falai/flux-dev-lora --input '{
  "prompt": "YouTube thumbnail style, close-up of a person with surprised excited expression looking at a glowing laptop screen, vibrant blue and orange color scheme, dramatic studio lighting, shallow depth of field, high contrast, cinematic",
  "width": 1280,
  "height": 720
}'

Specifications

Spec Value
Dimensions 1280 x 720 px (minimum)
Recommended 1920 x 1080 px
Aspect ratio 16:9
Max file size 2 MB
Formats JPG, GIF, PNG

The 120px Test

Your thumbnail appears at roughly 120px wide on mobile — that's how most viewers first see it.

At 120px, viewers must be able to identify:

  1. The mood/emotion (from colors and expression)
  2. The general subject (from composition)
  3. The text (if any — only if large enough)

Test: view your thumbnail at 120px width. If it's a muddy blur, redesign.

Safe Zones

┌─────────────────────────────────────────────┐
│                                             │
│   ✅ SAFE FOR TEXT AND KEY ELEMENTS         │
│                                             │
│                                             │
│                                             │
│                                             │
│                                       ┌───┐ │
│                                       │ ⏱ │ │ ← Timestamp overlay
│                              ┌────────┴───┘ │    (bottom-right)
│   ┌────┐                     │  DURATION    │
│   │ CH │ Chapter marker      └──────────────│
└───┴────┴────────────────────────────────────┘
     ↑ Bottom-left: chapter/progress markers

Avoid placing critical elements in:

  • Bottom-right corner (video duration timestamp)
  • Bottom-left corner (chapter markers, progress bar)
  • Extreme edges (cropping varies by device)

Color Strategy

High-Contrast Pairs That Work

Combination Mood Best For
Yellow + Black Urgency, attention Tech, business, lists
Red + White Energy, excitement Entertainment, reactions
Blue + Orange Professional contrast Education, tutorials
Green + White Growth, money Finance, success stories
Purple + Yellow Premium, creative Design, art, creativity
White + Dark Clean, minimal Luxury, minimalist channels

Color Rules

  • Background and text/subject should be complementary or high-contrast
  • Avoid same-temperature colors touching (red on orange = mud)
  • Use 3 colors maximum per thumbnail
  • Saturate more than real life — thumbnails compete with bright UI

Text on Thumbnails

When to Use Text

  • Lists/numbers: "7 Tips", "Top 10"
  • Strong opinions: "STOP Doing This"
  • Results: "$10K in 30 Days"
  • Comparisons: "vs" between two things

When NOT to Use Text

  • The video title already says it (redundant)
  • The emotion/visual tells the story
  • You can't make it large enough to read at 120px

Text Rules

Rule Reason
Max 6 words Readability at thumbnail size
Min 60pt equivalent Must be legible at 120px width
Bold sans-serif font Thin fonts disappear at small sizes
Contrast stroke/shadow Ensures readability on any background
No small text If it's not readable small, cut it

Face Expression Psychology

Thumbnails with faces get higher CTR than faceless thumbnails. Expression matters:

Expression CTR Impact Best For
Surprise/shock Highest Reaction, reveal, discovery content
Curiosity High Tutorial, how-to, tips
Excitement High Unboxing, reviews, announcements
Concern/worry Medium-high Warning, mistake, problem content
Confidence Medium Expert advice, authority content
Neutral Lowest Avoid unless your brand is minimalist

Face Composition Rules

  • Face should fill 30-50% of the thumbnail
  • Eyes looking toward the text or subject (directs viewer attention)
  • Eyes looking at camera = connection. Eyes looking at object = curiosity.
  • Place face on one side (usually left), text or subject on the other
bash
# Generate a face-forward thumbnail
infsh app run falai/flux-dev-lora --input '{
  "prompt": "close-up portrait of a man with genuinely surprised expression, mouth slightly open, raised eyebrows, looking at camera, left side of frame, vibrant teal background, dramatic rim lighting, YouTube thumbnail style, high contrast, cinematic",
  "width": 1280,
  "height": 720
}'

# Generate a face-looking-at-subject thumbnail
infsh app run bytedance/seedream-4-5 --input '{
  "prompt": "person looking amazed at a glowing holographic chart showing upward growth, dramatic blue and green lighting, right side profile view, dark background, tech aesthetic, high energy",
  "size": "2K"
}'

Thumbnail Patterns by Content Type

Tutorial / How-To

bash
infsh app run falai/flux-dev-lora --input '{
  "prompt": "overhead flat lay of organized workspace with laptop showing code editor, colorful sticky notes, coffee cup, clean bright background, professional setup, tutorial style composition, warm lighting",
  "width": 1280,
  "height": 720
}'

Before/After

bash
infsh app run falai/flux-dev-lora --input '{
  "prompt": "split composition, left side dark and messy disorganized desk, right side bright clean organized minimalist workspace, dramatic contrast between chaos and order, clear dividing line in center, high contrast",
  "width": 1280,
  "height": 720
}'

Product Review / Comparison

bash
infsh app run falai/flux-dev-lora --input '{
  "prompt": "two products facing each other with dramatic lighting and sparks between them, competition battle concept, dark background with colorful rim lighting, versus comparison style, high energy, product photography",
  "width": 1280,
  "height": 720
}'

Listicle / Number

bash
infsh app run falai/flux-dev-lora --input '{
  "prompt": "dynamic arrangement of 7 different colorful objects floating in space against dark gradient background, each item distinct and clearly separated, energetic composition, vibrant saturated colors, studio lighting",
  "width": 1280,
  "height": 720
}'

A/B Testing

Test one variable at a time:

Variable Test A vs B
Face vs No face Same composition, with/without person
Expression Surprise vs curiosity
Color scheme Warm vs cool palette
Text vs No text With/without text overlay
Background Bright vs dark
Composition Left-facing vs right-facing subject
bash
# Generate variant A
infsh app run falai/flux-dev-lora --input '{
  "prompt": "..., bright yellow background, ...",
  "width": 1280, "height": 720
}' --no-wait

# Generate variant B (same prompt, different background)
infsh app run falai/flux-dev-lora --input '{
  "prompt": "..., dark navy background, ...",
  "width": 1280, "height": 720
}' --no-wait

Thumbnail Checklist

  • 1280x720 minimum (1920x1080 preferred)
  • Under 2MB file size
  • Passes the 120px squint test
  • No critical elements in bottom-right (timestamp) or bottom-left (chapter)
  • Max 3 colors, high contrast
  • Text (if any) is max 6 words, bold, with contrast stroke
  • Face expression matches content energy (if applicable)
  • Doesn't duplicate the video title
  • Stands out from surrounding thumbnails (check your niche)
  • Works on both light and dark YouTube backgrounds

Common Mistakes

Mistake Problem Fix
Too much text Unreadable at thumbnail size Max 6 words or no text
Low contrast Disappears in the feed Use complementary colors
Cluttered composition Eye doesn't know where to look One focal point
Generic stock photo feel No personality, gets skipped Authentic expressions, unique angles
Tiny details Lost at 120px Bold, simple shapes
Same style every video Viewer fatigue Vary within brand guidelines
Misleading thumbnail Kills trust, hurts retention Match the actual content

Related Skills

bash
npx skills add inference-sh/skills@ai-image-generation
npx skills add inference-sh/skills@image-upscaling
npx skills add inference-sh/skills@prompt-engineering

Browse all apps: infsh app list

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