YouTube thumbnail size and specs, explained

The numbers

A YouTube thumbnail is 16:9, and the resolution YouTube recommends is now 3840 × 2160. The 1280 × 720 that every guide quotes is the previous recommendation: it is still accepted and still looks fine, because almost nothing is ever displayed above 720p anyway — but the documented target moved up when the file ceiling did. The minimum accepted width is 640 pixels.

The file size limit depends on where you upload from, and this is the number most advice still gets wrong: 50 MB from a computer, 2 MB from the phone, and 10 MB for a podcast thumbnail on mobile. The 2 MB that the whole internet quotes as the thumbnail limit is the mobile one. The accepted formats are JPG and PNG. YouTube's page on custom thumbnails is the source for all of it.

WebP is not on that list. Nor is BMP, and an animated GIF is refused because a thumbnail is a still image. If your export preset writes WebP — several editors default to it now — that is a file YouTube will not take, however good it looks.

Where your thumbnail actually appears

One image has to survive an eightfold range of sizes. On a desktop home feed it renders around 360 px wide; in search results on desktop, roughly the same. In a mobile feed it spans nearly the full width of the phone, which on most handsets is the largest it will ever be seen. In the suggested rail beside a playing video it drops to about 168 px, and on a channel page grid it sits near 210 px. Add end screens, embedded players and the TV app, and the same file is being asked to read clearly anywhere from 120 px to 1280 px. That range, not the upload spec, is the real design brief.

Why upload 1280 px for a 360 px slot

Almost nobody sees your thumbnail at full size. On a desktop home feed it renders around 360 px wide; in a mobile feed it is roughly the width of the phone; in the suggested rail it can be under 170 px. You still upload at 1280 px because YouTube generates every smaller version from that master file, and downscaling a large sharp image looks far better than upscaling a small one. Design big, judge small.

What YouTube does to your file after upload

Your upload is not what gets served. YouTube re-encodes it and generates a ladder of derivatives — commonly 1280 × 720, 640 × 480, 480 × 360, 320 × 180 and 120 × 90 — and serves whichever fits the surface, increasingly as WebP rather than your original format. Two consequences matter. First, re-encoding is lossy on top of your own compression, so anything already soft gets softer. Second, some of the legacy sizes are 4:3, which means a 16:9 image is letterboxed with black bars in those slots. You cannot control which variant a surface picks, so the safe move is to keep the design centred and never rely on the extreme left or right edge carrying meaning. What that re-encode does to a design — and why the file a viewer downloads is never the one you uploaded — is measured in the guide on blurry thumbnails. If the new image is stored but the old one keeps appearing, that is caching rather than processing: the guide on thumbnails that will not update has the header that explains it. The shape is a separate question from the resolution, and a file that is not 16:9 is fitted into the slot rather than refused — the aspect ratio guide covers what that costs you.

A 16:9 thumbnail on a vertical video

If the video itself is vertical and you give it a 16:9 custom thumbnail, YouTube does not letterbox it. On the home, explore and subscriptions pages it replaces your thumbnail with a 4:5 crop generated from the video — a frame you did not choose, in the three surfaces where most browsing happens. Your custom thumbnail still appears elsewhere, which is what makes this so easy to miss: the design looks correct everywhere you go to check it. If a video is vertical, treat the thumbnail as a vertical asset. The Shorts guide has the 9:16 spec and the surfaces it covers.

File size and format

JPG at high quality is the safe default for photographic thumbnails; PNG is worth it when you have hard-edged graphics or text on flat colour, where JPG artefacts show up around the letters. The 50 MB ceiling is not a target and never was. A 3840 × 2160 export at high JPEG quality lands somewhere between one and five megabytes — a tenth of the allowance at the very most — and what protects detail is exporting once at full resolution, not exporting heavy. Which of the two ceilings applies depends on the device you upload from, and that is the whole subject of the file size guide.

Text big enough to survive the downscale

There is a usable rule for text size. If your smallest text is at least a tenth of the image height, it stays legible everywhere the thumbnail appears. At 1280 × 720 that means a cap height of roughly 72 px — far larger than most people's instinct. Set a word at that size and it will still be readable at 168 px in the suggested rail, which is the hardest case. Anything under about 40 px at full resolution is decoration: it will be there, it will look considered in your editor, and no viewer will ever read it. The quickest way to check is to scale the whole canvas down to 15% and see what is left. The arithmetic behind that tenth, and how many words actually fit, is in the guide on text size.

The safe zones

Parts of your image are covered by the interface. The duration badge sits in the bottom-right corner. On a watched video, the red progress bar runs along the bottom edge. In some surfaces a "CC" or live badge appears bottom-left, and on mobile the title wraps immediately underneath, competing for attention. Keep faces, key objects and any text you need read out of the bottom strip — the bottom-right corner especially.

Dark mode and edges

Most viewing happens in dark mode. A thumbnail with dark, low-contrast edges bleeds into the background and loses its shape in the grid; a light or high-contrast edge keeps the frame readable. This is the single easiest thing to check in a realistic preview, and the single most common thing missed in an editor with a white canvas behind it.

Why an upload gets rejected

Custom thumbnails are not available on every account: the channel has to be verified by phone, and a live community-guidelines strike can suspend the privilege entirely. Beyond that, uploads fail for a short and predictable list of reasons — the file is over the limit for the device you are uploading from (50 MB on a computer, 2 MB on the phone), it is an animated GIF, it is narrower than 640 px, or it is in a format outside JPG and PNG. A file that is merely close to the limits is usually accepted and then re-encoded harder, which is worse than being rejected because nothing tells you it happened. The requirements have changed since most advice about this was written: the guide on the missing custom thumbnail option has the current list.

Quick checklist

• 3840 × 2160 px recommended, 16:9, minimum 640 px wide — 1280 × 720 is still accepted
• JPG or PNG, under 50 MB from a computer or 2 MB from the phone
• Nothing important in the bottom-right (duration badge) or along the bottom edge (progress bar)
• Readable at roughly 170 px wide — the suggested-rail size
• Still distinct against a dark background, not just on your editor's canvas
• Text short enough to read in one glance: three or four words at most

The questions everyone asks