In newer versions of Photoshop, at least since v2020, using the crop tool result in a new layer. This can be a nag if you’re just adjusting a jpeg file. It makes you flatten the image first before you save it again, if you don’t want to pass by the save dialog and choose the .jpg extension.
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It is simple to prevent this, in the Crop Tool options check Delete Cropped Pixels. That’s it.
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