Reference
YouTube Thumbnail Sizes Explained
YouTube generates up to five thumbnail files per video. Here's what each one actually is, in order from largest to smallest.
| Size | Dimensions | Availability |
|---|---|---|
| Maximum Available (maxresdefault) | 1280 × 720 | Only present if the uploader's source image supports it — check before assuming it exists. |
| SD (sddefault) | 640 × 480 | Standard definition, widely available. |
| HQ (hqdefault) | 480 × 360 | High quality; one of the most consistently available sizes. |
| MQ (mqdefault) | 320 × 180 | Medium quality, used in compact previews. |
| Default | 120 × 90 | Always generated — the guaranteed fallback. |
Why Resolutions Vary by Video
The 1280×720 "maximum available" file only exists when the uploader provided a high-resolution source thumbnail. Older videos, or ones uploaded at low resolution, may cap out at 640×480 or smaller. The 120×90 default image is the one guarantee — YouTube generates it for every public video, which is why tools use it as a fallback and as a way to detect an invalid video ID (a genuinely missing video returns only that placeholder-sized file).
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