How it works
The browser decodes the image locally and reports its natural width and height. The tool divides both numbers by their greatest common divisor to get the simplified ratio, then compares it with the standard ratios (16:9, 4:3, 3:2, 1:1, 9:16 and so on) to name the closest match. Because photos are often a few pixels off after cropping, the exact ratio is shown next to the nearest standard one.
Why the aspect ratio of an image matters
Uploading an image with the wrong ratio gets it cropped by the platform, often through the middle of a face or a logo. Knowing the ratio first lets you crop deliberately or pick a layout slot that fits. It is also the fastest way to check whether two images will line up in a grid, or whether a wallpaper matches your screen.
Privacy
Files are read with the browser's own image decoder and never leave your computer. There is no upload, no server, and no storage. Reloading the page clears everything.