Mastodon Image Resizer

The tool produces 1200 × 627 (1.91:1), 1200 × 800 (3:2), 1080 × 1350 (4:5), and 1500 × 500 (3:1) Profile Banner images. The first three are practical presets for regular Mastodon attachments. Mastodon does not require one universal aspect ratio for Post images, so choose the format that best matches your composition.

Choose 1.91:1 for a wide social post, 3:2 for a traditional photography composition, 4:5 for portraits and vertical designs, and 3:1 for a Profile Banner. If you are unsure, preview more than one format and choose the crop that keeps the most important content visible.

Your image is resized proportionally and cropped to fit the selected format. It is never stretched. The initial crop is centered automatically, so use Adjust if important content is near an edge.

Yes. Choose Adjust beneath a preview, then drag the image or use the arrow keys to reposition it. Choose Apply crop when the composition looks right. Each target format has its own crop, so changing one preview does not change the others.

Images without transparency are downloaded as JPEG files for smaller file sizes. Images with an alpha channel are downloaded as PNG files so transparent areas remain intact, including transparent WebP uploads.

No. This tool does not save processed images to your account or create a media library entry. Images are processed for the resize operation and returned to your browser for download. You should still avoid uploading sensitive images to any online service.

Mastodon limits can vary between instances. Administrators may configure different maximum file sizes, supported formats, and media-processing behavior. These presets use practical dimensions for regular attachments and a 1500 × 500 profile banner target, but they do not guarantee that every instance will accept every file.