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Drop your thumbnail in and see what YouTube does to it: the crop, the resample, the file type, and whether it clears the size limit for where you are uploading from. The file never leaves your browser.
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Every row above without a qualifier is YouTube's own published figure. Checked against YouTube Help on 22 September 2026.
A YouTube thumbnail size checker answers a question a size guide cannot: not what the number is, but what happens to your file. Drop a thumbnail in and the browser reads its dimensions, compares them to 16:9, and draws the crop on your own frame. Nothing is uploaded and no account is needed.
The number itself has moved, which is the other reason to check. YouTube now recommends 3840 x 2160, and most of the pages ranking for this term still print 1280 x 720 as the answer. That figure is not wrong, it is the floor, and on a television the difference shows.
The browser decodes the image and reads its width and height. That is the only thing the arithmetic needs, which is why nothing is sent anywhere.
YouTube crops to 16:9 before it resizes, so the shape is judged before the scale. A 4000 x 3000 export is a crop problem, and fixing the resolution would not save the part that gets cut.
If the shape is wrong, the area YouTube discards is dimmed on your own image and the percentage is printed next to it.
Every feed placement prints the video length over the bottom right in a solid box. That strip is marked so you can see whether your design collides with it.
One line, with the current recommendation rather than the one a 2019 guide printed.
One checker per surface. Every one runs in your browser, nothing is uploaded, and none of them wants an account.
See the 9:16 crop and the safe zones the profile row and reply box cover, drawn on your own story. Nothing is uploaded.
Try it free 📘Facebook crops covers differently on desktop and mobile. See both crops and the area that survives them. Nothing is uploaded.
Try it free 💼See the 4:1 crop, the 15 percent mobile cut and where your profile photo lands on your banner. Nothing is uploaded.
Try it free 📐Every surface in one table, each figure dated against the platform own page, with a checker per surface.
Try it freeA thumbnail is the only part of a video that competes in the feed, and it is the part most likely to be quietly altered on the way in. Two things go wrong, and neither is visible in your design tool.
The limit is 2 MB in the mobile app and 50 MB from a computer, and the formats accepted are JPG and PNG only. A webp export decodes perfectly in your browser and is refused on upload, which is the failure with no error message attached to it.
Anything that is not 16:9 is cut to fit from the middle. On a design with a face to one side, that is the face.
Most pages answering this question still print 1280 x 720. Exporting to that today gives you a thumbnail that holds up in a feed and falls apart on a 4K panel.
The number moved. Your old export did not.
Most pages answering this question were written when 1280 x 720 was the recommendation and have never been opened since. Check the date on any size guide before you trust its figure, including this one.
For years the answer was 1280 x 720, and it was right. A thumbnail was a small tile in a feed on a phone, and 720p carried everything that tile could show. YouTube has since raised the recommendation to 3840 x 2160, because a thumbnail is no longer only that tile: it is the poster frame on a television, the still on a watch page, the preview inside an embed on somebody else’s site. Fine text and small faces that held together at 1280 wide come apart on a 4K panel.
The reason so many pages still print the old number is the reason this one keeps its figures in a single file and dates them. A spec typed into a sentence has no way of noticing that it changed. It sits there collecting links and looking authoritative, and the more links it collects the longer it survives being wrong. Treat 1280 x 720 as the floor, export at 4K, and let the file size be the thing you manage. The same trap catches every platform, which is why the table of every surface carries the date each figure was last read off the platform itself.
Start on the 4K canvas rather than scaling up at the end. Upscaling a 1280 wide design gives you a 4K file with 720p detail: the size of the new spec and the sharpness of the old one.
The duration badge lands there in every feed placement. The checker shades it on your own frame.
The same frame as a JPG lands far inside the limit with no loss visible at any size anyone will view it, and JPG is one of the two types YouTube accepts.
There it compresses better than JPG and keeps the edges clean. That is the one case where PNG is both smaller and sharper.
Before you find out on the watch page.
The thumbnail is the whole click decision and there is no design team to catch a bad export. One check before upload.
A template fixes the layout and not the export settings. This catches the webp export and the oversized PNG that will be refused.
It is almost always the file type or the size rather than the dimensions, and the checker says which.
Every check returns the same four things, so the answer is the same shape whichever file you drop in.
One line saying what YouTube does to this exact file, before you upload it.
The part the platform throws away, dimmed on your frame, with the percentage of the frame it costs.
The area the platform covers with its own interface, hatched, with a dashed box around what survives.
The size to export instead, and the 16:9 shape to build on so the crop never happens.
3840 x 2160 pixels at 16:9. YouTube raised its recommendation to that 4K figure, replacing the 1280 x 720 most guides still print. 1280 x 720 still works and is now the practical floor, with an absolute minimum width of 640 pixels.
Almost always the file size rather than the dimensions. The limit is 2 MB from a computer, and a detailed 4K PNG goes over it without looking like it should. Export the same frame as a JPG at around quality 80 and it lands well under.
Up to 3840 x 2160, yes, because that is what YouTube now serves to large screens. Beyond it, no: the file is resampled down and you have moved the resampling from your own tool, where you can see it, to a compressor you do not control.
16:9, with no tolerance. Anything else is cropped to fit, centred, and you do not get to choose the framing. Drop the file into the checker above and it draws the cut before you upload.
JPG and PNG, and nothing else. JPG is the right default at 4K because it stays inside the size limit comfortably. PNG is better for thumbnails that are mostly flat colour and hard-edged type. A webp file decodes perfectly in a browser and is refused on upload, which is worth checking before you find out.
Getting to 3840 x 2160 is an export setting, and it takes one afternoon to fix forever. The harder problem is knowing which hook to put on the frame this week, and the week after. Selzee reads your comments, reviews and post results, turns them into concepts worth making, and learns from what each one does.
The checker is free, with no signup and no credit card. When you want the idea on the thumbnail to come from your own audience rather than a guess, start free.
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Keep exploring: the Instagram story checker, every other surface, the Instagram feed checker, the Instagram size guide.
