Convert format
Choose images and an output format. JPG has no transparency, so transparent areas become white; PNG does not use the quality slider.
Crop / rotate
Drag a crop box on the preview and check the crop size shown. You can rotate left or right or restore the full image; rotating resets the crop box.
Compress image
Choose JPG or WebP, adjust the quality, check the processed preview and actual size, then download. If the output is larger than the original you'll be told clearly; converting to PNG does not guarantee a smaller file.