What this canvas actually does
Freeform versus a locked ratio
Freeform lets you pull any rectangle. The other four presets lock aspect so the box cannot skew. Switching a preset recenters a 90% box on the current image. That is a react-image-crop handle job, not a width×height form — numeric sizes are the pixels spoke.
The five presets on this toolbar
Freeform (no ratio). Square 1:1 labeled Instagram Post. Portrait 4:5 labeled Instagram Portrait. Landscape 16:9 labeled YouTube Thumbnail. Facebook Post at 1.91:1. This page does not add Stories 9:16, LinkedIn banners, or TikTok slots — those belong on the Instagram and social spoke.
Same container on download
JPEG stays JPEG, PNG stays PNG, WebP stays WebP. A second JPEG encode can add artifacts; graphics are safer as PNG. The crop discards pixels outside the box. It does not resize to a listed pixel pair and does not compress for a kilobyte cap.
Stills only in this dropzone
JPG, JPEG, PNG, and WebP. HEIC, BMP, TIFF, AVIF, and GIF sequences are convert-first or rasterize-first on other Convertify4u tools, then return here with a still the browser can paint.