Zellio.io

Image Resizer

Resize any image to exact pixels or a percentage — no upload.

Processed locally — nothing is uploaded

About Image Resizer

Downscaling discards pixels for good, and scaling back up cannot recover them, so always start from the largest original you have. At identical dimensions WebP typically saves another quarter over JPEG.

This image resizer changes the pixel dimensions of a PNG, JPEG or WebP image to an exact size or a percentage of the original, with an optional aspect-ratio lock so the result never looks stretched. Resize down for faster-loading web images and thumbnails, or hit precise dimensions required by an upload form or ad slot.

There is no round trip to a server, so the result appears as quickly as your device can draw it. Export as PNG, JPG or WebP — at matching dimensions WebP is usually the smallest of the three for the same visible quality.

Learn how this works

How to Edit Images in the Browser Without Uploading ThemCompress, watermark and strip metadata from photos entirely on your device — why client-side image editing is faster and more private.8 min readPNG, JPEG, WebP or SVG: How to Choose an Image FormatA practical guide to picking the right image format — what each one is good at, where each falls down, and how to decide quickly.6 min read

Frequently asked questions

Are my images uploaded to resize them?

No. Everything runs locally in your browser using standard web APIs — your text, files and inputs are never uploaded to a server, so the tool works even offline once the page has loaded.

Will resizing distort my image?

Not if you keep the aspect-ratio lock on — changing the width updates the height (and vice-versa) so the proportions are preserved. Unlock it only if you intend to stretch to exact dimensions. With the lock enabled, resizing proportionally maintains the original look even if the pixel count changes, which is ideal for creating thumbnails or fitting images into responsive grids. Unlocking the ratio lets you crop or stretch an image to exact specifications when needed, though this may distort the original for extreme aspect-ratio changes.

Which output formats are available?

You can download the resized image as PNG (lossless), JPG (smaller, for photos) or WebP (modern, efficient).

Related tools

Image CompressorShrink PNG & JPEG files to a target size — one at a time or in batches.Favicon GeneratorTurn any image into favicon.ico plus all the PNG sizes you need.Aspect Ratio CalculatorFind the ratio of any width and height, and resize while keeping it.