Find the largest thumbnail YouTube provides
The chosen image may be served as JPEG or another web image format such as WebP, depending on the URL YouTube exposes. Image dimensions and format can be checked after saving if a design workflow requires a specific asset. A thumbnail's resolution is independent of the video's 1080p or 4K stream, and the image can be lower resolution than the video. Paste a supported video URL, preview the returned image, and use the save control to download the best source thumbnail that is actually available.
A video thumbnail is a still image, not a frame extracted by re-encoding the downloaded video. YTMetadata resolves the image URLs associated with the video and prefers the largest suitable available thumbnail. YouTube's maxresdefault.jpg is commonly 1280 × 720, but not every upload has that asset; older or less common videos may expose only a smaller sddefault or hqdefault image. The tool uses an available source image rather than enlarging a small thumbnail and presenting it as genuine HD.