The safest all-around YouTube thumbnail size is 1280×720 (16:9). For Shorts, use 1080×1920 (9:16). Square posts on IG often perform well at 1080×1080 (1:1).
Recommended presets
- YouTube: 1280×720 (JPG or PNG)
- Shorts/TikTok/Reels: 1080×1920
- Instagram square: 1080×1080
Need commands or exact crop guidance? Use the Aspect Ratio Converter for ffmpeg recipes, or the Thumbnail Resizer for quick exports with safe-area overlays.