What is the biggest YouTube thumbnail size?

1280×720, served as maxresdefault.jpg. YouTube does not store anything larger, so any tool advertising a "4K thumbnail download" is upscaling.

Why does maxresdefault return a 404?

Because YouTube never generated one for that video. It is only produced when the source upload was high enough resolution. Older and low-quality uploads simply do not have it. hqdefault.jpg is the only size guaranteed to exist for every video.

What are hq1, hq2 and hq3?

Auto-captured stills from roughly 25%, 50% and 75% of the way through the video. YouTube generates them as candidate thumbnails to offer the uploader. They are the only genuine video frames exposed by a plain URL.

What size should I upload for my own thumbnail?

1280×720 (16:9), under 2 MB, as JPG, PNG, GIF or WebP. YouTube downscales from there to produce every other size. Uploading larger gains nothing; uploading smaller means you never get a maxresdefault.

YouTube thumbnail sizes and URLs

A complete reference to the thumbnail files YouTube generates for every upload. Verified against live responses, not copied from older articles.

Free toolYouTube Thumbnail DownloaderEvery thumbnail size YouTube generates, up to 1280×720 HD, plus its auto-captured frames. Black bars trimmed off.Open the downloader

The URL pattern

Every thumbnail lives at a predictable address:

https://i.ytimg.com/vi/VIDEO_ID/NAME.jpg

For the video ID dQw4w9WgXcQ, the HD thumbnail is therefore https://i.ytimg.com/vi/dQw4w9WgXcQ/maxresdefault.jpg. The host img.youtube.com serves the identical files and is interchangeable.

WebP versions exist under a different path, /vi_webp/VIDEO_ID/NAME.webp. They are typically 25 to 35% smaller at the same visual quality.

Every size

Name	Resolution	Aspect	Always exists?	Black bars?
`maxresdefault`	1280×720	16:9	No	No
`sddefault`	640×480	4:3	No	Yes
`hqdefault`	480×360	4:3	Yes	Yes
`mqdefault`	320×180	16:9	Yes	No
`default`	120×90	4:3	Yes	Yes
`hq1 / hq2 / hq3`	480×360	4:3	Usually	Yes
`mq1 / mq2 / mq3`	320×180	16:9	Usually	No

The black bar problem

Anything listed as 4:3 above is not really a 4:3 image. It is a 16:9 frame padded with solid black above and below to fill a 4:3 box. It is a holdover from when YouTube's own layout was 4:3.

So hqdefault.jpg is nominally 480×360, but only the middle 480×270 is picture. If you drop it into a 16:9 layout you get bars inside bars. Either crop it yourself, or use the thumbnail downloader with Trim black bars enabled. It scans for the actual content edges and crops them off before saving.

Scanning beats assuming: a video that is not exactly 16:9 gets bars of a different thickness, and a hard-coded 45-pixel crop would be wrong for it.

Which one should you use?

Publishing or presenting. Use maxresdefault, falling back to a de-barred hqdefault.
A list or grid of videos. Use mqdefault. It is clean 16:9, always present, and tiny.
You want an actual moment from the video. hq1 to hq3 are your only URL-accessible frames. For a specific timestamp you need Live Capture or the file extractor.

Uploading your own thumbnail

Resolution: 1280×720, minimum width 640px
Aspect ratio: 16:9
Formats: JPG, PNG, GIF or WebP
Maximum file size: 2 MB

Everything else is derived from this one image. Upload below 1280×720 and YouTube will never produce a maxresdefault for your video.