Image resizer

How to use it

1. 1

   Drop the images

   Several at once is fine. Each one keeps its own original size, listed underneath with the size it is heading for.

2. 2

   Set any one of the three numbers

   Width, height or scale per cent. With the ratio locked the other two follow, so a 900 by 600 photograph typed to 450 wide becomes 450 by 300.

3. 3

   Or fit into a known size

   The list holds current social, icon and print sizes. Print entries are worked out at the PPI you choose in the advanced options.

4. 4

   Download

   Each image is redrawn in the page and saved with its new pixel size in the file name, so nothing is guesswork later.

Three numbers, one decision

Every resizer asks for a width and a height. That hides the fact that the useful question is often the third number: how much of the original am I keeping? Putting width, height and scale side by side and keeping them linked means you can think in whichever unit the job is stated in. A designer says 1080 pixels wide. A print shop says A4 at 300 PPI. Somebody trimming a page says half the size. All three are the same operation.

Why the downscale is stepped

The canvas specification does not say which resampling algorithm a browser must use when it draws an image smaller, and most engines use a cheap filter that falls apart on a big reduction. Going from 4000 pixels to 400 in one draw drops detail and adds aliasing. Halving repeatedly and only then making the final small step keeps each reduction inside the range that filter handles well. That is the default here, and it is why the result is sharper than a single pass.

Fit, fill or stretch

When the shape you ask for does not match the shape of the picture, something has to give. Fit keeps the whole picture and lands inside your box, so a 3 by 2 photograph asked for a square comes out shorter than the square. Fill reaches the box exactly and trims the overflow evenly from the middle. Stretch reaches the box exactly and distorts everybody in the frame. The default is fit, because it is the only one that never surprises you.

Your image never leaves the page

The file is read by your browser and drawn onto a canvas in this tab. There is no upload, no account and no server to store anything, which you can confirm in your browser's network tab: choose a file and watch nothing happen. That matters for the ordinary case where the picture is a product shot before launch, a screenshot with customer data in it, or somebody's photograph you were trusted with.