Zellio.io

Image Resizer

Resize one image or fifty — exact pixels, percentages, and presets you keep.

Runs locallyWorks offlineShare link carries settings, never your data
Send output toImage CompressorFavicon GeneratorAspect Ratio CalculatorBuild a workflow from thisOutput stays on this page until you send it.

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), or keep whatever format each file arrived in — useful in a batch of mixed types.

Can I resize a whole folder at once?

Yes. Choose or drop up to fifty images and one set of settings applies to all of them, with each row showing what that particular file will become before you run anything. A single image downloads on its own; several arrive as one ZIP, each named after the size it was written at so the files sort sensibly in a folder.

Where are the presets I save kept?

In this browser's local storage on this device, under a key belonging to this site. They are never uploaded and are not tied to an account, so clearing site data removes them and a second device will not see them. Each one holds the mode, the numbers, the output format and the quality. A link copied from the page carries those same settings, which is the way to move one to another machine or another person.

What is the difference between Fit inside and Fill and crop?

Fit inside scales until the whole picture sits within the box, so one edge usually finishes shorter than the number you typed and nothing is discarded. Fill and crop gives you the box exactly by trimming the overflow from the centre, which is what a fixed social slot needs. Exact size forces both numbers and stretches to reach them, and is the one to avoid on anything containing a face, a logo or a straight line.

Why will it not make my image bigger?

Enlarging stays off until you tick Allow enlarging, because scaling up cannot restore detail that was never captured — the result is a softer copy at a larger file size. With the box ticked, a batch still only enlarges the files that need it, so the small images in a mixed folder are not blurred up to match the others.

Pro tips

  • Keep the aspect-ratio lock on unless you have a specific reason to distort; entering both numbers by hand is the usual cause of a subtly squashed logo.
  • Resize before compressing. Discarding pixels you will never display costs nothing visually and does more for file size than lowering quality on an oversized image.
  • Always work from the largest original you still have — enlarging an export invents detail that was never captured and looks smeared.
  • For anything going on the web, export WebP; at matching dimensions it is usually the smallest of the three formats at the same visible quality.
  • Check the result at the size it will actually be displayed, not zoomed in. Softness that is obvious at 400% is invisible in place.
  • For a batch shot both ways round, use Longest edge: one number keeps every file inside the same bound whichever orientation it was taken in.
  • Save the sizes a client or a marketplace keeps asking for, then start from the chip instead of retyping two numbers and choosing a mode every time.

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.

Two numbers decide how an image looks on a modern screen, and only one of them is the size you type here. A layout slot measured at 400 CSS pixels is drawn with 800 or 1,200 device pixels on a phone or a high-density laptop, so an image exported at exactly 400 looks soft on most hardware sold in the last decade. Export at roughly twice the slot width and the file still shrinks dramatically from a camera original.

Fitting a shape that is not your image's shape is a separate decision from size. Changing width and height independently stretches faces and text in a way viewers notice immediately without being able to name it. When the target shape differs from the source, crop to the ratio first and resize second.

Resizing is also the cheapest accessibility and performance win available on most pages. An oversized image costs mobile visitors real money on metered connections and delays the largest contentful paint that search engines measure, and neither cost is visible to whoever uploaded it on a fast office connection. Checking the dimensions of what you are publishing against the space it occupies takes seconds and is routinely the single largest saving on a slow page.

Fifty files can go through one setting in a single pass. Drop a folder's worth and the table fills with every picture's current measurements beside what it will become, so a mistake is visible before anything is written; press the button and the whole queue arrives as a ZIP whose file names carry their new measurements. A batch of mixed portrait and landscape shots is exactly why the longest-edge option exists, since one number then bounds every photo without sorting them by orientation first. Anything the browser cannot decode marks its own row and the remaining files carry on.

The awkward part of this job is rarely the arithmetic, it is remembering which numbers a particular destination demands. The picker holds the platform slots worth maintaining — story frames, link previews, video thumbnails, banner strips — and beside it sits a box for naming whatever combination you have just dialled in, which then reappears as a chip on every later visit. Those saved entries stay in this browser, and saving a second one under an existing name replaces it rather than piling up near-duplicates. Copy link puts the same settings into a URL, so two people can agree on an export target without writing a document about it.

Common use cases

  • Bloggers shrinking camera photos to a theme's content width so pages stop loading multi-megabyte images nobody sees at full size.
  • Sellers meeting a marketplace's exact pixel requirements for a listing photo without opening a desktop editor.
  • Developers producing @1x and @2x assets for an interface from a single high-resolution source.
  • Job applicants resizing a headshot to the dimensions a portal demands before it will accept the upload.
  • Anyone preparing an email signature or forum avatar that has to sit inside a fixed box without being cropped by the platform.
  • A photographer putting a whole shoot through one web width and collecting the results as a single archive.
  • A team settling on one export size by passing round the tool's link, which carries the settings and none of the pictures.
How it comparesA desktop editor like Photoshop or GIMP gives finer resampling control and scripted actions with per-file rules, and takes minutes to open for a job that takes seconds; fifty files through one setting need no install and no licence here. Compared with upload-based resizers, the difference is that the picture is never handed to anyone — which matters more for a passport scan than a product shot, and more again when the folder is somebody else's photographs.