ガイド
YouTubeサムネイルのサイズを解説
YouTubeで取得できる主なサムネイルサイズと使い分けを紹介します。
サムネイルには複数サイズがあります。用途に合うサイズを選ぶと確認精度が上がります。
Why multiple sizes exist
YouTube serves different thumbnail sizes for different surfaces.
That is why one image can look sharp on desktop but soft in another context.
Common sizes you will see
Most extractors show default, medium, high, and max-resolution variants.
Not every video has every size, especially older uploads.
- Default: fast preview.
- Medium/High: general review.
- Max resolution: best for detail checks.
How to pick the right one
If you are inspecting typography or small details, start with the largest option.
If you only need a quick visual reference in notes, a medium size is often fine.
Quality check tips
Zoom to inspect edges and text clarity before using a thumbnail as inspiration.
If quality is weak at source, do not expect perfect results after resizing.
Useful for
- Checking image sharpness before analysis.
- Preparing visual audits for a channel.
- Selecting the best reference size for slides.
Always compare size before reuse
Use the largest available image for quality checks, then scale down only if needed.