Get Reddit thumbnails right the first time
Reddit shows your image in several places — a tiny card thumbnail in compact feeds, a larger preview when a post expands, and a cover frame for video. Each slot has its own size and aspect-ratio expectation. This tool gives you the correct source dimensions per content type and lets you verify your own asset before upload, so nothing gets cropped or rejected.
How it works
Pick a content type and the tool returns Reddit’s recommended source size, the ideal aspect ratio, accepted file formats, and the maximum file size. If you paste in your own width and height, it reduces them to a simplified ratio and compares against the target, flagging when your image will be cropped or letterboxed.
The ratio simplifier uses the greatest common divisor of width and height, so 1920 × 1080 is reported as 16:9 rather than a long decimal.
Reference at a glance
- Link / image post preview: 1200 × 628 px, 1.91:1, up to 20 MB
- Square image post: 1080 × 1080 px, 1:1, up to 20 MB
- Native video cover: 1280 × 720 px, 16:9, up to 10 MB
- Vertical / short video: 1080 × 1920 px, 9:16, up to 10 MB
- Promoted post (ad): 1200 × 628 px, 1.91:1, up to 5 MB
Tips
Design to the largest preview and let Reddit downscale for the card thumbnail — a sharp 1200 px source still reads cleanly at 70 px. Keep logos and headlines inside the centre two-thirds so they survive aggressive feed crops, and stay well under the file-size cap to avoid Reddit re-compressing your image and softening fine detail.