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Free web tool

Thumbnail Competitor Tester

A thumbnail is never seen alone — it's seen in a grid, next to the videos it competes with. The tester at vidai.help/thumbnail_tester puts your candidates into that grid with the real top-performing videos for your topic, so you judge them the way a viewer will — before you publish.

Why it helps

Most thumbnail advice is about the image in isolation: contrast, faces, big text. What actually decides the click is relative — does yours stand out next to the eight thumbnails around it, at the size a phone shows it? The tester answers that in a minute, with no uploads and no credits.

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Real competitors

Live YouTube search for your topic fills up to 11 slots with the videos already winning it — not stock placeholders.

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The size that matters

A one-click mobile preview shrinks the feed to phone proportions, where most clicks happen and most text becomes unreadable.

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Nothing leaves your browser

Your images are kept in the browser only. VidAI calls YouTube for competitor thumbnails and titles — never with your files.

How to use it

  1. Open the tester and sign in

    Go to vidai.help/thumbnail_tester and sign in with Google. Not signed in? The landing page has a demo feed with sample competitors you can drop your images into — good for a first look, but the opponents aren't real.

  2. Add 1–5 thumbnail ideas

    Drop JPG, PNG or WebP files up to 2 MB each. They're held in your browser (not uploaded), and your progress is kept until you press Start over.

  3. Describe your topic

    One line, the way a viewer would search: "sourdough for beginners", "budget gaming PC 2026". VidAI searches YouTube and lists similar high-performing videos (Shorts excluded) — untick any you don't want, or paste a YouTube URL to add a specific opponent. Results are saved in your browser for 24 hours; Refresh search asks YouTube again.

  4. Read the feed

    Your thumbnail appears in the test slot of a YouTube-style home grid among the real cards. Switch between your candidates, flip the mobile preview, try light and dark. Download the opponents' thumbnails if you want to study them side by side.

  5. Iterate

    Edit the image, drop the new version in, compare again. Start over clears everything — images, topic and opponents — when you're done.

What to look for: does yours read at a glance next to the neighbours? Is the face or subject large enough at phone size? Four words of text or fewer? Does the colour clash with — rather than blend into — the cards around it? If it disappears in the grid, it will disappear on YouTube.
Cost: free — the tester uses 0 credits on every plan, including the free one. It's a web tool, so it works without the Chrome extension. Ukrainian version: vidai.help/uk/thumbnail_tester.

✅ What you get

  • Your thumbnail judged in context — the grid, not a blank canvas.
  • The real competition for your topic, at desktop and phone size.
  • A minute-long loop: drop, compare, edit, repeat — free.