Correction, 2026-10-02: an earlier version gave 640 pixels as the minimum width for Shorts thumbnails. YouTube's minimum for Shorts is 640 pixels tall; the 640-pixel minimum width is for video thumbnails. It also left out that Shorts thumbnails can only be added in YouTube Studio on a computer, used an old title for the help page, said "many guides" still quote 1280 x 720 (that was YouTube's own recommendation in 2025, now cited from an archived copy), and named the 6-credit image models without the labels the model picker shows (Seedream 5 Lite, Nano Banana Standard). All YouTube figures were re-checked on 2026-10-02.
YouTube's help page now asks for custom thumbnails at 3840 x 2160 pixels for videos and 2160 x 3840 for Shorts, at least 640 pixels wide for videos and at least 640 pixels tall for Shorts, as JPG or PNG. The file can be up to 50 MB when you upload from a desktop, but a video thumbnail uploaded from the mobile app is capped at 2 MB, and Shorts thumbnails can only be added in YouTube Studio on a computer. The 1280 x 720 and 2 MB figures that YouTube's own page gave in 2025 are out of date. And custom thumbnails need a verified account.
TL;DR
| Requirement | Videos | Shorts |
|---|---|---|
| Recommended resolution | 3840 x 2160 | 2160 x 3840 |
| Aspect ratio | 16:9 | 9:16 |
| Minimum | 640 px wide | 640 px tall |
| Formats | JPG or PNG | JPG or PNG |
| Maximum file size | 50 MB on desktop, 2 MB on mobile | 50 MB on desktop |
| Where to add it | Desktop or mobile app | YouTube Studio on a computer only |
| Who can upload | Verified accounts | Verified accounts |
All from YouTube Help, "Add custom thumbnails on YouTube", checked 2026-10-02.
What changed, and what it means
In mid-2025 the same help page recommended 1280 x 720 and a 2 MB limit. Since then the recommended resolution went up to 4K, the desktop size limit went up to 50 MB, and Shorts got their own 9:16 size. The minimum stayed low: 640 pixels wide for videos, 640 pixels tall for Shorts. In practice:
- Make it 16:9 at 3840 x 2160 if you can. YouTube asks for an image as large as possible, since it is also the preview image in the embedded player.
- 1920 x 1080 meets the minimum. It is just not the recommended size.
- Upload from a desktop. The mobile app caps video thumbnails at 2 MB, and Shorts thumbnails cannot be added there at all.
- Give vertical videos a 9:16 thumbnail. On a vertical video, YouTube replaces a 16:9 custom thumbnail with an auto-generated 4:5 one on the home, explore and subscription pages.
- Verify the account first. Without verification, you choose from YouTube's auto-generated suggestions.
Making a thumbnail with AI
A thumbnail is three things: a subject that reads at small size, a background, and usually a few words. Image models can misspell words, so check the lettering hardest and split the job.
- Generate the image without the text. On 8frame, Seedream 5 Lite or Nano Banana Standard, at 6 credits each, are cheap enough to generate a dozen options and pick one.
- Add the words. Either set them yourself in any editor, which is exact and free, or use Nano Banana Pro at 21 credits, the model we recommend when words must be spelled right; details in best AI image generator for text. Keep it to two to four words either way.
- Get to 3840 x 2160. If the image comes out smaller, enlarge it: on 8frame, BRIA Increase Resolution is 6 credits for a content-preserving 2x or 4x (up to 8192 x 8192), and Clarity, which always enlarges 2x and is diffusion-based, is 13. Check faces and lettering at full size afterwards, since upscalers can alter both.
- Export JPG or PNG under 50 MB and upload from a desktop.
A dozen candidate images at 6 credits and one Nano Banana Pro text pass at 21 come to 93 credits on 8frame, under $1 at pack rate; a BRIA upscale adds 6. The free route is compared in best free AI thumbnail makers.
Reading at small size
Feeds and phone screens show a thumbnail at a fraction of the size you upload. Before uploading, shrink your thumbnail to about the width of a fingertip on screen and check:
- Is the subject still recognisable?
- Can you read the words?
- Is there one clear focal point, or three competing ones?
If the answer to any of these is no, a bigger resolution will not fix it; try a simpler composition.
FAQ
What is the YouTube thumbnail size in 2026? 3840 x 2160 pixels (16:9) for videos and 2160 x 3840 (9:16) for Shorts, with a minimum of 640 pixels wide for videos and 640 pixels tall for Shorts, per YouTube Help on 2026-10-02.
What is the maximum YouTube thumbnail file size? 50 MB when uploading from a desktop, 2 MB for a video thumbnail from the mobile app. Shorts thumbnails can only be added in YouTube Studio on a computer.
Is 1280 x 720 still OK for a YouTube thumbnail? It meets the 640-pixel minimum width, but YouTube now recommends 3840 x 2160. 1280 x 720 was its recommendation in 2025.
Why can't I upload a custom thumbnail? Custom thumbnails need a verified account; unverified accounts choose from auto-generated options. Shorts thumbnails also need YouTube Studio on a computer. And there is a daily limit per channel: if you see "Daily custom thumbnail limit reached", try again in 24 hours.
What format should a YouTube thumbnail be? JPG or PNG.
Sources
- YouTube Help, "Add custom thumbnails on YouTube": resolution 3840 x 2160 for videos and 2160 x 3840 for Shorts, minimum width 640 pixels for videos and minimum height 640 pixels for Shorts, 16:9 and 9:16, JPG or PNG, 50 MB on desktop and 2 MB on mobile for video thumbnails, Shorts thumbnails only in YouTube Studio on a computer, 16:9 thumbnails on vertical videos replaced by an auto-generated 4:5 one on the home, explore and subscription pages, verified accounts, daily limit (try again in 24 hours): support.google.com/youtube/answer/72431, checked 2026-10-02
- The same page in 2025, recommending 1280 x 720 and a 2 MB limit: archived copy of 2025-06-06, checked 2026-10-02
- 8frame prices (Seedream 5 Lite 6, Nano Banana Standard 6, Nano Banana Pro 21, BRIA Increase Resolution 6 for 2x or 4x up to 8192 x 8192, Clarity 13 at a fixed 2x): the 8frame app, checked 2026-10-02
Generate the picture, set the words, upload from a desktop.
Try it without signing up: the 8frame canvas opens on a real board. The canvas is free and unlimited; generation is paid from $19/month.