vidpickr

Glossary · concept

What is Thumbnail (video preview image)?

A thumbnail is the static preview image shown for a video before it plays — in search results, on the homepage, in subscription feeds. YouTube generates six thumbnail sizes per video and serves them from the i.ytimg.com CDN. The largest is 1280×720 (maxresdefault.jpg) and only exists when the uploader provided a custom HD thumbnail.

Also called:video thumbnail · preview image · maxresdefault

Every public YouTube video has up to six standard thumbnail files at fixed sizes. The full set, in descending resolution: maxresdefault (1280×720, only if custom thumbnail uploaded), hq720 (1280×720, auto-generated on newer videos), sddefault (640×480), hqdefault (480×360, always present), mqdefault (320×180), default (120×90).

YouTube does not natively serve thumbnails above 1280×720. Tools that advertise "4K thumbnails" are upscaling the 720p file — the underlying pixel data is the same as the maxres source.

Thumbnails are available via the public i.ytimg.com CDN with no authentication. The URL pattern is https://i.ytimg.com/vi/{videoId}/{size}.jpg (or .webp for WebP variants from vi_webp/). Anyone can save them, including via our [/youtube-thumbnail-downloader](/youtube-thumbnail-downloader) tool.

Common questions

Why don't some videos have a maxres thumbnail?
maxresdefault.jpg only exists when the uploader provided a custom HD thumbnail. Auto-generated thumbnails from the video itself only go up to hqdefault (480×360). hq720.jpg is YouTube's newer auto-generated 720p variant, present for most newer uploads but not for older content.
Can I download a thumbnail in 4K?
YouTube doesn't store thumbnails above 1280×720. "4K thumbnail" services upscale the existing 720p file — same content, slightly bigger pixels, no extra detail.

Related terms

Metadata (video file metadata)

Metadata is the information about a video file that isn't the audio or video data itself — title, artist, duration, resolution, codec used, encoding date, GPS location, thumbnail.

CDN (Content Delivery Network)

A CDN (Content Delivery Network) is a globally distributed network of servers that caches content close to viewers, reducing latency and offloading traffic from origin servers.

VidPickr is a free, browser-based YouTube downloader. Every term in this glossary either describes how YouTube delivers video or why your downloads behave the way they do. Try the downloader →