Image Resizer

This image resizer changes the pixel dimensions of PNG, JPG, WebP, GIF, BMP and AVIF images directly in your browser. It is for anyone who needs a photo to fit an upload form, an email, a website or a social-media slot, and it handles up to 50 images at once without sending any of them to a server.

There are four ways to set the size. By percentage scales both sides by the same factor: 25% turns a 4032 × 3024 phone photo into 1008 × 756. By width sets the width and works out the height from the aspect ratio, so 1200 px wide gives 1200 × 900 for that photo; by height does the same the other way round. Exact size takes a width and a height. With "Keep aspect ratio" the image is fitted inside that box without distortion or cropping — a 1920 × 1080 image fitted into 1080 × 1080 comes out 1080 × 608 — and with "Stretch" it fills the box exactly, distorting the picture if the shapes differ. Sizes are rounded to the nearest whole pixel and never drop below 1 px.

How it works: your browser decodes each image with its own codecs (phone photos are turned upright using their EXIF orientation), draws it onto a canvas at the new size and encodes the result. When an image shrinks by more than half, it is scaled down in halving steps before the final draw, with the browser's high-quality smoothing — one big jump samples too few pixels and produces jagged edges and moiré. Enlarging is allowed (up to 1000%), but it only interpolates: the picture gets more pixels, not more detail, and each enlarged result says so.

"Same as input" keeps PNG as PNG, JPG as JPG and WebP as WebP. GIF, BMP and AVIF are saved as PNG, because browsers can read those formats but cannot reliably write them. You can also pick JPG, PNG or WebP explicitly; JPG and WebP use the quality slider (85 by default), and because JPG has no transparency, transparent areas are filled with the colour you choose. An animated GIF is resized as its first frame only. EXIF metadata (camera, GPS, date) and embedded colour profiles are not copied to the output.

Limits: each file can be up to 50 MB, and an output can be at most 16,384 px on a side and 100 megapixels, which is where browser tabs start running out of memory. iPhones and iPads have a lower canvas limit of about 16.7 megapixels, so very large outputs may fail there with a message saying so.

If you need a smaller file rather than fewer pixels, use the image compressor instead; if you need a different format at the same size, use one of the converters.

Your images stay on your device. They are read into the page's memory, resized there and offered back as downloads. You can confirm it in your browser's developer tools: the Network tab shows no request carrying your files.

1. Each file's first bytes are checked to confirm it really is PNG, JPG, WebP, GIF, BMP or AVIF, whatever its name says. 2. The browser decodes it (createImageBitmap, applying EXIF orientation) to get its true width w and height h. 3. The new size is computed: percentage → (w × p/100, h × p/100); by width W → (W, h × W/w); by height H → (w × H/h, H); exact with keep aspect → scale = min(W/w, H/h), then (w × scale, h × scale); exact with stretch → (W, H). Every side is rounded to the nearest pixel, with a minimum of 1. 4. The output is checked against the canvas limit (16,384 px per side, 100 megapixels) and flagged as enlarged if either side grew. 5. The image is drawn onto a canvas at the new size with high-quality smoothing, halving in steps first when shrinking by more than 2×. For JPG output a background colour is painted first. 6. The canvas is encoded as PNG, JPG or WebP and named after the original with the new size appended, e.g. holiday-1200x900.jpg.