"What size should a YouTube thumbnail be?" sounds like it has one answer, but there are really two. One is the size of the image you upload as a creator. The other is the set of sizes YouTube creates and serves to viewers on different screens. Mixing them up leads to blurry thumbnails, and to confusion when a downloader shows five different images for one video. This guide covers both, using YouTube's own help pages (checked in October 2026) and our own checks of YouTube's image server.
What to upload: YouTube's current recommendations
YouTube's help page on custom thumbnails recommends uploading the largest image you can, because the same image is used as the preview in the embedded player. At the time of writing, YouTube recommends:
| Regular videos | Shorts | |
|---|---|---|
| Recommended resolution | 3840 × 2160 px | 2160 × 3840 px |
| Minimum | 640 px wide | 640 px tall |
| Aspect ratio | 16:9 | 9:16 |
| Formats | Image formats such as JPG or PNG | |
| File size limit | 2 MB when uploading from a phone; 50 MB from a computer | |
Older guides, including an earlier version of this page, quote 1280 × 720, and many still give 2 MB as the only file limit. Those figures were YouTube's advice for years, and 1280 × 720 still matters in one place: YouTube's A/B testing feature says that if any test thumbnail is below 720p (1280 × 720), all the thumbnails in that test are scaled down to 480p. So 1280 × 720 is a sensible floor, and 3840 × 2160 is the current recommendation.
To upload a custom thumbnail at all, your YouTube account has to be verified. You add or change it in YouTube Studio under Content, then the video's details, then Thumbnail. Custom thumbnails must follow YouTube's Community Guidelines. A thumbnail that breaks them can be removed and can lead to a strike.
What YouTube serves: the five standard sizes
Whatever you upload, YouTube produces smaller copies for search results, suggestions, embeds and slow connections. Every video has a set of predictable image addresses on YouTube's image server. These are the five our thumbnail downloader checks, with the sizes we got back when we checked 11 videos in October 2026:
| File | Pixels | Shape | Notes |
|---|---|---|---|
maxresdefault.jpg | 1280 × 720 | 16:9 | Largest standard copy. Missing for some videos. |
sddefault.jpg | 640 × 480 | 4:3 | Black bars above and below a 16:9 picture. Missing for some videos. |
hqdefault.jpg | 480 × 360 | 4:3 | Black bars as above. Present for almost every video. |
mqdefault.jpg | 320 × 180 | 16:9 | Small but bar-free. |
default.jpg | 120 × 90 | 4:3 | Tiny preview. |
Notice that the largest standard copy is 1280 × 720, even though YouTube now recommends uploading at 3840 × 2160. The 4K upload isn't wasted (see below), but don't expect to download a 4K thumbnail from these public addresses.
YouTube doesn't publish documentation for these file names. They're simply the addresses its own pages use. The list above is what we observed, and YouTube could change it at any time.
Why upload large if YouTube shows it small?
There are good reasons to follow the "as large as possible" advice:
- Big screens. Thumbnails appear on TVs and large monitors, and as the poster frame of the embedded player before someone presses play. A small upload gets stretched and looks soft.
- Future-proofing. YouTube makes its copies from your original. If it adds larger display sizes later, a high-resolution original gives it something to work from.
- Your own archive. Keep your full-size master file (ideally the layered design file too). You can't get the original back from YouTube's public copies.
The practical limit is file size. If you upload from a phone, a 3840 × 2160 PNG can easily exceed 2 MB. Export as a high-quality JPG, or upload from a computer, where the limit is 50 MB.
Aspect ratio and the 4:3 sizes
Design regular video thumbnails at 16:9. That is the ratio of the player and of most places thumbnails appear. If you upload a different shape, YouTube has to fit it into a 16:9 frame.
The two 4:3 files (sddefault and hqdefault) are a leftover from YouTube's early 4:3 days. For a normal 16:9 video they contain the whole picture with black bars above and below. If you download one and need a clean 16:9 image, crop the bars off: from the 480 × 360 file you'll get roughly 480 × 270.
File format and file size
YouTube's help mentions JPG and PNG. In practice:
- JPG is best for photographic thumbnails. A high-quality setting keeps files small with little visible loss.
- PNG keeps sharp edges on text and flat graphics, but files are much larger. Watch the 2 MB mobile limit.
Whatever you upload, the copies YouTube serves from its image server are JPGs. That's why everything our downloader saves is a .jpg file.
Shorts and podcasts
Shorts thumbnails follow the vertical recommendation above: 9:16, ideally 2160 × 3840. YouTube's help says custom Shorts thumbnails can currently only be added in YouTube Studio on a computer, and only by verified accounts. Our Shorts thumbnails guide covers this in detail, including how vertical and horizontal thumbnails get swapped in different parts of the app.
For podcast playlists, YouTube asks for a square 1:1 image rather than 16:9.
Quick checklist
- Design at 16:9 for videos (9:16 for Shorts).
- Export at 3840 × 2160 if you can, and never below 1280 × 720 if you plan to A/B test.
- JPG for photos, PNG for flat graphics. Keep it under 2 MB if uploading from a phone.
- Check it at small sizes. Most people see your thumbnail at a fraction of its real size (see our design tips).
- Keep your original master file. YouTube's public copies top out at 1280 × 720.
Sources: YouTube Help, "Add customised thumbnails on YouTube" and "A/B test titles and thumbnails" (both checked 22 October 2026). Served sizes were measured by GrabYTthumb on the same date. YouTube updates its specifications from time to time, so check its help pages before relying on any limit.