ThumbProof
Export horizontal thumbnails at 16:9, at least 1280×720 pixels (the current help center recommends going as large as 3840×2160), as JPG or PNG. Keep the file under 2 MB so it also uploads from a phone; desktop uploads accept up to 50 MB. Vertical Shorts covers use 9:16, ideally 1080×1920 or larger. Then check the design at 168×94 pixels and keep the bottom-right corner free of text and faces, because the duration badge sits there.
The official numbers in one table
Platform help pages change every year or two, so start from the source. The current help center page for custom thumbnails recommends making the image “as large as possible” because it is also used as the preview image in the embedded player. It sets a minimum width of 640 pixels for horizontal videos and a minimum height of 640 pixels for vertical Shorts.
The upload limit is the number that causes the most failed uploads. It depends on the device: phones are limited to 2 MB for a video thumbnail, while desktop uploads now accept much larger files. Because many creators finish and upload from a phone, 2 MB is still the safe target for every export.
“Have a resolution of 3840 x 2160 pixels for videos and 2160 x 3840 for Shorts, with a minimum width of 640 pixels for videos and a minimum height of 640 pixels for Shorts.”
Add custom thumbnails — video platform help center
| Item | Horizontal video | Vertical Short |
|---|---|---|
| Aspect ratio | 16:9 | 9:16 |
| Recommended size | 3840×2160 (1280×720 is the classic minimum standard) | 2160×3840 (1080×1920 is fine) |
| Minimum | 640 px wide | 640 px tall |
| Formats | JPG or PNG | JPG or PNG |
| Size limit, mobile upload | 2 MB | 2 MB |
| Size limit, desktop upload | 50 MB | 50 MB |
Why 1280×720 is still the working standard
For years the published recommendation was exactly 1280×720 pixels, and it remains the most practical master size. It has enough detail for a full-width desktop feed, it is a clean multiple of every common display size, and a photographic JPEG at this size usually lands between 150 and 450 KB, far under any limit.
Going to 1920×1080 or 3840×2160 makes sense when the same image is reused as the large preview in an embedded player or on a TV, where the frame is wide enough to show the extra detail. The trade-off is file weight. A 4K JPEG at quality 85 is often 1.5 to 4 MB, which breaks the 2 MB mobile limit unless you compress it. If you export at 4K, keep a 1280×720 or 1920×1080 copy for phone uploads.
| Export size | Pixels | Typical JPEG (q85) | Typical PNG | Under 2 MB? |
|---|---|---|---|---|
| 1280×720 | 0.92 MP | 150–450 KB | 0.8–2.5 MB | JPEG yes, PNG often not |
| 1920×1080 | 2.07 MP | 300–900 KB | 2–5 MB | JPEG yes |
| 3840×2160 | 8.29 MP | 1.5–4 MB | 8–20 MB | Only with compression |
The PNG column is the usual surprise. PNG is lossless, so a photo-like thumbnail with gradients and faces compresses badly. Use PNG only for flat graphics with large areas of solid color, and use JPEG or WebP-converted-to-JPEG for everything else.
Every size your thumbnail is actually shown at
Almost nobody sees your thumbnail at 1280×720. Responsive layouts scale it down to fit the grid, the phone screen or a narrow column next to the player. The table below lists the display sizes ThumbProof previews. They are approximations of common layouts rather than official figures, and they shift by a few pixels with screen width, but they are close enough to judge legibility.
| Where it appears | Approx. display size | Share of the 1280×720 master | What to check |
|---|---|---|---|
| Large desktop grid | 360×202 | 28% of the width | Title text and faces still crisp |
| Mobile feed, full width | ~360×202 (CSS px) | 28% | The image dominates the screen, so detail helps |
| Search results list | 320×180 / 246×138 | 19–25% | Competes with text snippets beside it |
| Up next / sidebar | 168×94 | 13% | The hardest test: one subject, few words |
| Playlist / small lists | 120×68 | 9% | Only shapes and colors survive |
At 168×94 your 1280×720 master is reduced to about 2% of its original pixel count. Text that is 40 pixels tall on the canvas becomes roughly 5 pixels tall, which is unreadable. That is why the rule of thumb is to make the smallest important text at least 90–110 pixels tall on a 720-pixel-high canvas.
How to export a thumbnail that passes every check
- 01
Set the canvas
Create a 16:9 document at 1280×720 or 1920×1080 (or 1080×1920 for a vertical cover) in sRGB.
- 02
Mark the safe zones
Add guides at 78% of the width and 78% of the height, and a 50-pixel margin. Keep text and faces out of the corner.
- 03
Design for 168×94
Zoom your editor to about 13% and check that the subject and the main word are still clear.
- 04
Export as JPEG q85
Use sRGB, strip metadata, and check the file size. Aim for under 2 MB, ideally under 1 MB.
- 05
Resize or compress if needed
Run oversized files through the resizer with the 1280×720 preset and “Keep the file under 2 MB” switched on.
- 06
Preview in a feed
Drop the export into the feed preview and the safe zone checker before you upload.
Safe zones: the parts of the frame you lose
The interface draws on top of your image. On horizontal videos the duration badge sits in the bottom-right corner, and a red progress bar can appear along the bottom edge for videos the viewer has partly watched. On hover, desktop feeds can show small icons in the top-right corner, and some layouts start an inline preview that replaces the thumbnail completely after a moment.
ThumbProof treats the right-hand 22% of the width and the bottom 22% of the height as the badge corner. Keep text, faces and logos out of that rectangle. Keep the bottom 5% free of anything important because of the progress bar, and leave a margin of about 4% around every edge, because some layouts crop or round the corners.
| Zone | Covered by | On a 1280×720 canvas | Rule |
|---|---|---|---|
| Bottom-right corner | Duration badge | x > 1000, y > 560 | No text, faces or logos |
| Bottom strip | Progress bar | y > 684 | Nothing essential |
| Top-right corner | Hover icons | x > 1150, y < 120 | Avoid small details |
| Outer margin | Rounded corners, crops | ~50 px on each edge | Keep text inside |
Vertical covers and the 4:5 swap
Vertical covers have their own crops. The full-screen player shows the whole 9:16 frame, but the bottom third is covered by the caption, the channel name and the sound label, and the right edge carries the like, comment and share buttons. Profile and shelf grids often crop the cover to 4:5 or even 1:1 from the center.
One detail from the help center is easy to miss: vertical videos that were given a 16:9 custom thumbnail can have it replaced by an auto-generated 4:5 frame on some home and subscription surfaces. If a video is vertical, give it a proper 9:16 cover and keep the subject in the middle 60% of the height.
“Vertical videos with 16:9 custom thumbnails will be replaced by an auto-generated 4:5 thumbnail on the home, explore, and subscription pages.”
Add custom thumbnails — video platform help center
Format, color and compression settings that work
Export in sRGB. Wide-gamut profiles such as Display P3 can look washed out or oversaturated once a browser or app converts them. Turn off embedded metadata you do not need, which trims a few kilobytes, and avoid CMYK files entirely.
For JPEG, a quality setting between 80 and 90 is the sweet spot. Below 75 you start to see blocky artifacts around text edges and faces, which is exactly where viewers look. Chroma subsampling (4:2:0) can blur thin red or blue text; if your text is saturated and thin, export at 4:4:4 or make the strokes thicker. If a file is over 2 MB, reduce quality before reducing resolution, and never go below 1280×720 for a horizontal thumbnail.
Worked example: fixing a 6.8 MB export
A creator exports a 3840×2160 PNG straight from a design app. The file is 6.8 MB, so the phone upload fails. The audit also flags the bottom-right corner, because the word “FINAL” sits under where the duration badge will be.
The fix takes three moves. First, convert to JPEG at quality 85, which brings the 4K file to about 2.6 MB, still too big for a phone. Second, resize to 1920×1080, which lands at roughly 780 KB with no visible loss at feed sizes. Third, move “FINAL” up and to the left by about 180 pixels. The corner meter turns green and the file uploads from any device.
| Step | Size | Format | File | Corner check |
|---|---|---|---|---|
| Original | 3840×2160 | PNG | 6.8 MB | Busy |
| Convert | 3840×2160 | JPEG q85 | 2.6 MB | Busy |
| Resize | 1920×1080 | JPEG q85 | 0.78 MB | Busy |
| Move text | 1920×1080 | JPEG q85 | 0.79 MB | Clear |
Common thumbnail size mistakes
Exporting PNG photos
Lossless PNG files of photos are huge. Use JPEG for anything with faces, gradients or textures.
Using the wrong ratio
A 4:3 or 1:1 image gets letterboxed or cropped. Always export exactly 16:9 or 9:16.
Text under the duration badge
The bottom-right corner is covered on almost every surface. Move key text up and to the left.
Judging at full size only
A design that works at 1280×720 can turn to mush at 168×94. Always check the smallest size.
Upscaling a small frame
Enlarging a 640-pixel screenshot to 1280 adds blur, not detail. Start from a sharp source.
Forgetting the phone limit
Desktop accepts 50 MB, but the 2 MB mobile limit will bite the day you upload from your phone.
High-CTR Thumbnail Checklist: 7 Visual Principles That Get Noticed
Title Truncation by Device: Pixel Widths, Not Character Counts
Thumbnail Color and Contrast: Standing Out in Dark and Light Feeds
Thumbnail Text: How Many Words, How Big, and Where to Put Them
Faces and Focal Point: Making One Thing Impossible to Miss