Free YouTube Thumbnail Checker

Check your thumbnail before it goes live.

Upload up to 3 thumbnail variants, enter the video title, preview them in YouTube-style layouts, and get a local readiness score before publishing.

FreeNo sign-upPrivateBrowser-onlyUp to 3 variants
Images never upload

Upload a thumbnail

JPG, PNG, or WebP. Analysis stays in your browser.

Recommended YouTube thumbnail format: 1280 x 720, 16:9, under 2 MB.
Color analysis uses the open-source fast-average-color browser library.
Compare up to 3 variants without uploading thumbnails to a server.

Used locally for title rewrites. It is not uploaded.

Readiness score
--Upload first

The score combines YouTube format fit, contrast, sharpness, edge crowding, and title fit. It is a preview heuristic, not a CTR guarantee.

Why this score

ThumbAudit scores avoidable packaging risks before upload. It is a readiness check, not a guaranteed CTR prediction.

Local QA

Format fit

22% weight

Checks 1280 x 720, 16:9 framing, and YouTube-friendly file size.

Visual contrast

22% weight

Looks for enough light and color separation to survive mobile feeds.

Sharpness

22% weight

Flags soft screenshots, low-detail exports, and blurry focal points.

Title fit

18% weight

Checks whether the video title can wrap clearly in YouTube previews.

Edge crowding

16% weight

Penalizes busy borders where overlays, timestamps, and crops compete.

Preview lab

Compare how the thumbnail reads across common YouTube surfaces.

Desktop home feed

Upload a thumbnail

I redesigned my YouTube thumbnail and the click-through rate changed fast

Creator channel

48K views · 2 hours ago

Mobile preview

Upload a thumbnail

I redesigned my YouTube thumbnail and the click-through rate changed fast

Creator channel · 48K views

Publishing checklist

0 of 3 checks are ready.

45%

Upload image

Waiting for thumbnail

Enter title

Preview wraps live

Review previews

Desktop, search, watch, mobile

Local title coach

Free title rewrites run locally. AI review can become the Pro layer.

99/100
Title fit99
Characters73/72 target
Suggested titles
I redesigned my YouTube thumbnail and the click-through rate...
I tested creator compares old against so you do not have to
Creator compares old against: what changed after the redesign
AI workflow signals

The free checker runs locally. These upgrade actions measure paid intent before model calls are enabled.

Free + Pro

Run a thumbnail check first to make AI review and exports useful.

Improve with AICreative review, title rewrites, and stronger hooks.ProCompare variantsJudge multiple thumbnail options before publishing.ProExport reportSave a client-ready checklist for each thumbnail.Studio

What the score checks

The checker looks at practical signals creators can fix before publishing: YouTube export format, visual contrast, image sharpness, edge crowding, and how the title wraps in previews.

Upload image

Ready in the first screen.

Enter title

Ready in the first screen.

Preview layout

Ready in the first screen.

Share result

Ready in the first screen.

Actionable fixes

Every suggestion is based on the uploaded image and title. The tool does not predict YouTube CTR; it catches avoidable preview problems before your audience sees them.

Use a 16:9 frame so the thumbnail does not crop oddly.

Make the subject readable at mobile feed size.

Keep large text short and away from busy edges.

Compare the thumbnail against the title before publishing.

YouTube thumbnail checker FAQ

Is the uploaded thumbnail sent to a server?

No. The image is read with browser APIs and analyzed locally. Shared links include the score and title, not the uploaded image.

What size should a YouTube thumbnail be?

YouTube recommends 1280 x 720 pixels, a 16:9 aspect ratio, and a file under 2 MB.

Does this predict CTR?

No. It is a readiness score for visible thumbnail issues. Actual CTR depends on audience, topic, packaging, and competition.

What does the score measure?

The score combines format fit, contrast, sharpness, edge crowding, and title fit so you can catch avoidable packaging problems.

Can I compare multiple thumbnails?

Yes. Upload up to 3 variants, select the active version, and the score, preview, checklist, and share link update locally.

Can I use it on mobile?

Yes. The upload control works on mobile browsers, and the preview includes a mobile feed-style frame.

Can I share the result?

Yes. Use Copy or Share after analysis to generate a result URL without uploading the image.

Does this replace YouTube A/B testing?

No. Use this as a pre-publish QA step. Live A/B tests are still useful when you need audience-backed experiment data.

Is this affiliated with YouTube?

No. YouTube is a trademark of Google LLC. This is an independent creator tool.