Image dimensions determine how much space a picture can fill. File size measures something different: the bytes needed to store it. Resizing is useful when a photograph contains far more pixels than a page or form needs, but choosing both dimensions without considering proportions can distort the subject.
Understand the two dimension fields
Choose your JPEG, PNG, or WebP files and check the upload previews. Enter the desired width in pixels. Leave height at 0 to calculate it from each source image’s proportions. This is the easiest option when a group contains both landscape and portrait pictures.
Entering a positive height forces that exact width and height. The tool scales the whole image into that rectangle; it does not crop away excess edges. Use this only when those proportions are intentional. If a square is required, crop to a square first rather than squeezing a wide photograph.
The output is PNG. Width and height must remain within 1–16,384 pixels, and the result must contain no more than 40 megapixels. Large dimensions can exceed the pixel limit even when neither side reaches the maximum.
Calculate a result before processing
For a 3000 by 2000 pixel photograph, set width to 1200 and height to 0. The height calculation is 1200 × 2000 ÷ 3000, producing an 800 pixel result. The composition stays the same because both dimensions scale by the same factor.
Now consider a 2000 by 3000 portrait in that batch. The same settings produce 1200 by 1800 pixels. A shared width does not create a shared height. If your destination requires every picture to be 1200 by 800, prepare crops that match that ratio before resizing.
Process the selection, compare the thumbnails, and download individual results or the ZIP. Inspect lettering and fine lines in a downloaded file, because a thumbnail can hide softness.
Keep a suitable source
Up to 20 files can share the settings. Each input must stay within 20 MB and 40 megapixels, with combined input/output limited to 100 MB. Smaller batches help when the browser runs short of memory.
Upscaling adds pixels but cannot recover absent detail. PNG output also may be larger than a compressed JPEG source. Canvas processing can remove metadata or color profiles and flattens animation; retain original files. Processing remains in your browser. Use Image Cropper to change composition, then Image Compressor if the resized result still exceeds your byte allowance.