The Crop Image is a free online tool that lets you drag a box, crop, and export. Everything happens locally in your browser using HTML5 Canvas, so your photos are never uploaded to a server, there's no file-size limit tied to an account, and there's nothing to sign up for.
How to use the Crop Image
Drop an image into the box below, or click it to browse your device.
Adjust the settings until the live preview looks right.
Click Download to save the result to your device — nothing ever leaves your browser.