Crop an image without uploading it

Almost every crop is a removal. A face, a house number, a colleague's monitor, the rest of the desk, the bystander at the edge of the frame. That makes cropping a redaction task, and a redaction task is the single worst candidate for an upload, because the version you send contains precisely the thing you were trying to take out.

The good news is that cropping actually works, which is not true of every method people reach for. Drawing a black box over something in a document editor often leaves the content underneath intact; cropping removes the pixels from the output. What it does not touch is the metadata block, so a photo whose GPS coordinates you cropped a landmark out of still names the place.

The fixed ratios exist because destinations are fixed. Use 1:1 for avatars, 16:9 for slides, 9:16 and 2:3 for phone screens and stories, 4:3 and 3:2 when matching existing photography. Rotation and flips are there for pictures of documents shot at an angle, though a flip mirrors any text in the frame, so use rotation on anything with words in it.

Verify it the way you would verify a redaction: crop, then open the saved result on its own and look at what is actually in the file, not at the editor's preview. Do the whole operation with the network disconnected and you have also proved that the uncropped original never left your machine.