Resize an image without uploading it

Fit, or exactly

Give a box in pixels. With fit inside the box the photo is scaled until it fits, keeping its proportions: a 4000 × 3000 photo in a 1920 × 1920 box comes out 1920 × 1440. With exactly this size it is made that wide and that tall, stretched if the proportions differ. The buttons fill in the box for you — half, a quarter, or a longest side of 2560, 1920, 1280 or 800 pixels — and while the lock is on, typing one side fills in the other in proportion to the picked photo.

Never enlarge is on by default: a photo already smaller than the box is written at its own size, and the card says so. Turn it off to scale up. The developer, in the first tab, resizes the other way — by a long edge, a width, a height or a percentage — together with the format, in one pass.

A whole folder of photos

Add many photos and press Resize all. Every photo is fitted into the same box, each keeping its own proportions, so portrait and landscape pictures both come out right. The results download one by one or together as a ZIP, written in the page.

How it is done

The picture is decoded by your browser, following its Orientation tag, and drawn on a canvas of the new size with the browser’s high-quality smoothing asked for. When the photo is not turned by its Orientation and is being made smaller, the page asks the decoder for the smaller size directly, so the full-size picture never has to sit on a canvas — which is what lets a large photo be reduced on a device whose canvas could not hold it whole. Where that is not possible, a big reduction is drawn in two steps, which aliases less than one.

What comes out

By default the new file has the format of the old one — JPEG stays JPEG, PNG stays PNG, WebP stays WebP where the browser can write it — or you can choose. Anything else, a HEIC for instance, is written as JPEG. For JPEG, WebP and AVIF the quality slider applies. Resizing is a re-encode: the new file carries none of the original’s metadata, its colours are converted to sRGB, and the original’s ICC profile is not carried over. The file name says the new size, so beach.jpg becomes beach-1920x1440.jpg.

Limits

The largest picture a browser can draw is set by the browser and the device. If the size you ask for is past that, the page says so and writes nothing. Pictures over 100 megapixels are not decoded. A photo the browser cannot decode cannot be resized here; its metadata can still be read in the Exif viewer. If you only want the metadata gone and the pixels left exactly as they are, do not resize: remove the EXIF data losslessly instead.

How to check that nothing is uploaded. The page’s own scripts make one request of their own — the sample card, from this site, when you press for it — and none that carries a file. The folder is served with a Content-Security-Policy header that lets the page connect only to this site and to Google’s analytics hosts, so even a mistake here could not send a photo anywhere else: the browser would refuse it. Open the developer tools, choose the Network tab, clear it, then add a photo and run the tool, and watch. Google’s analytics counts the visit and that a tool was used; nothing in this page hands it a file name, a pixel or a tag.