optimizationA/B Simulator

YouTube Thumbnail Tester & A/B Feed Simulator

Test and preview multiple thumbnail concepts side-by-side in real YouTube desktop, mobile, sidebar, and search feeds.

YouTube Thumbnail Tester (A/B Test Simulator)

Upload multiple thumbnail concepts and preview them side-by-side inside realistic YouTube feeds before uploading.

MediaCube-Style A/B Simulator
Thumbnail A (Primary)
Variant A
Thumbnail B (Challenger)
Variant B
Thumbnail C (Optional)
Click to Add 3rd ThumbnailTest 3 variants at once

A/B CTR Performance Scoreboard

Automated visual contrast, mobile legibility, and focal point simplicity benchmarking.

Winner: Variant B (87/100)
Variant A
Variant A14:28
Overall CTR Potential:84/100
Contrast76%
Mobile View96%
Simplicity81%
Variant BTop Performer
Variant B14:28
Overall CTR Potential:87/100
Contrast96%
Mobile View83%
Simplicity82%
YouTube View Layout:
Variant:
YOUTUBE PREVIEW • VARIANT A • HOME
Safe-Zone: Active (Bottom Right)
Your Video14:28Your Video (Variant A)
C
I Tested 50 Side Hustles in 30 Days (The Brutal Truth)
Creator Labs
420K views•3 days ago
How I Built a $100K/Mo Business in 60 Days18:42
A
How I Built a $100K/Mo Business in 60 Days
Alex Hormozi Fans
1.2M views•1 week ago
The AI Revolution Nobody Is Prepared For22:15
C
The AI Revolution Nobody Is Prepared For
ColdFusion
890K views•4 days ago

Important Note

Smchecker Thumbnail Tester is an independent simulation and analysis tool. Thumbnails are rendered locally in your browser to simulate YouTube feed layouts.

How This Tool Works

1Upload 2 or 3 thumbnail concepts or paste YouTube video links to inspect.
2Enter your video title, channel name, and duration to render a complete YouTube video card mockup.
3Switch between Desktop Home Feed, Mobile App Feed, Up Next Sidebar, and Search Results views.
4Toggle Dark and Light theme previews and check the bottom-right timestamp safe-zone clearance.

Frequently Asked Questions — YouTube Thumbnail Tester

Viewers make split-second decisions when scrolling YouTube feeds. Previewing your thumbnail alongside competing viral videos helps you spot whether your colors pop, text is legible at mobile size, and focal points command attention.

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