Two crops, and you only ever see one
Whatever sits near the left and right edges is visible on desktop and gone on mobile. Whatever sits near the top and bottom is the other way round.
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Facebook crops your cover differently on desktop and on mobile. Drop your file in and see both crops and the area that survives them, on your own design.
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Every row above without a qualifier is Facebook's own published figure. Checked against Facebook's Help Center on 22 September 2026.
A Facebook cover is the one surface where a single number cannot describe what happens. It displays at 820 x 312 on a desktop browser and 640 x 360 on a phone, and those are different shapes rather than one shape at two scales.
So Facebook cuts a different piece out of your artwork depending on who is looking. Drop a file in and the checker marks both crops on your own image, so you can see which half of your layout is only visible to half your audience.
Read off the decoded image in your browser. Nothing is uploaded and no account is needed.
851 x 315 is what Facebook asks you to upload, so that is what a file is measured against rather than either display size.
The desktop view is shorter and the mobile view is narrower. Each is drawn on your frame so the difference is visible rather than described.
Roughly the middle 640 x 312 survives on every screen. That is the area your logo and headline have to sit inside.
JPG and PNG, and the checker says which yours is before Facebook does.
One checker per surface. Every one runs in your browser, nothing is uploaded, and none of them wants an account.
Drop a thumbnail in and see what YouTube does to it, against the current 3840 x 2160 spec. Nothing is uploaded.
Try it free 📱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 💼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 freeCovers fail in a way that is invisible to the person who made them, because designers check the device they designed on.
Whatever sits near the left and right edges is visible on desktop and gone on mobile. Whatever sits near the top and bottom is the other way round.
Facebook asks for 851 x 315 under 100 KB, and recompresses whatever you send. Handing it a file at display size leaves nothing spare for that pass.
An sRGB JPG survives that pass more gracefully than a PNG of the same photograph, which is a format decision rather than a size one.
Two crops, one file, and you only ever check one.
Designers build covers on the device they are holding. The other half of your audience is looking at a different rectangle of the same picture.
Almost everything written about Facebook cover photos leads with a single number, and a single number cannot describe this surface. A cover is shown at 820 x 312 in a desktop browser and 640 x 360 on a phone. Those are not the same rectangle scaled up and down, they are different proportions, so Facebook cuts a different piece out of your artwork for each audience.
Facebook's own recommendation, 851 x 315, matches neither display exactly. It is larger than both, which is the point: it leaves headroom for the crop rather than handing the platform a file with none. The rule is the one that governs every surface with more than one crop: design for the overlap, let the imagery bleed, and keep anything that has to be read in the middle. A LinkedIn banner fails the same way for a different reason, and the full table says which other surfaces carry a safe area at all.
851 x 315 is Facebook's own recommendation and it carries headroom over the 820 x 312 desktop view. Give Facebook exactly the display size and there is nothing spare, which is what looks soft on a high-DPI screen.
That rectangle is inside both crops. The checker draws it on your own file.
Photography behind a crop still reads as photography. Only type and marks need to respect the safe area.
Facebook re-compresses covers hard, and a JPG survives that pass more gracefully.
There the edges stay clean where a JPG would smear them, and the file is usually smaller too.
No designer to catch the mobile crop, and the cover is the first thing a visitor sees.
One check before handover beats a revision round after somebody opens it on a phone.
It is not a bug and it is not your export. It is a different crop, and this shows you where it lands.
Every check returns the same four things, so the answer has the same shape whichever file you drop in.
One line saying what Facebook does to this exact file, before you upload it.
Every thing wrong with the file, not the first one. A file can be the wrong type and the wrong size at once.
Both device crops drawn on your own image, and the overlap that survives them.
What to re-export, and where a re-export will not help because the detail is not in the source.
It displays at 820 x 312 pixels on desktop and 640 x 360 on mobile. Upload at 851 x 315, which is what Facebook asks for, as an sRGB JPG under 100 KB.
Because it is a different crop, not a different scale. Desktop shows a wider, shorter rectangle and mobile shows a narrower, taller one. Anything outside the overlap of those two is visible to some people and not to others.
Roughly the middle 640 x 312 pixels, the area inside both the desktop and the mobile crop. Keep your logo, your headline and anything you need read inside it.
JPG in sRGB for photographic covers, because Facebook re-compresses covers hard and a JPG survives that pass more gracefully. PNG for covers that are mostly flat colour and hard-edged type, where the edges stay clean.
No. An event cover is a wider shape at roughly 1.91:1, and a page cover dropped into an event loses a lot of its height. The safe-zone principle is the same: design for the area that survives every crop.
Sizing a cover takes one export and then it is done. Knowing what the page should say to the people who land on it, this month and next, is the part that stalls. Selzee reads your reviews, comments 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 page under the cover to work as hard as the cover does, start free.
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Keep exploring: the LinkedIn banner checker, the YouTube thumbnail checker, every other surface, the Instagram size checker.