If a slightly crooked horizon has ever bothered you, the new Image Rotate & Straighten tool is for you. Level a tilted photo in 0.1° steps, and handle 90° turns and horizontal or vertical flips on the same screen.
Turn on the grid lines to line up the horizon by eye, and choose what happens to the empty corners left by tilting: crop them away, fill them with white or leave them transparent. Save the result as JPG, PNG or WEBP. Your photo is processed only in your browser and never uploaded.