Image Resizer: Resize Images Online by Pixels or Percent

How to use the image resizer

To resize an image, upload it, type the width you want with "Lock aspect ratio" switched on, and the matching height is calculated for you. Download the result. Reducing a 4000 px photo to 1200 px typically cuts the file size by about 90%.

Load an imageDrag and drop, browse, or paste. The current dimensions appear immediately.
Enter the new sizeType a width or height with the ratio locked, or use the 25% / 50% / 75% shortcuts.
Pick a fit and downloadChoose cover, contain or stretch, then save your resized image.

About this tool

Resizing is the most effective way to make an image smaller: halving both dimensions removes three quarters of the pixels. This tool resizes with progressive halving: the image is reduced in steps rather than in one jump, which avoids the aliasing you get from a naive single-pass scale.

Choose how the image should fill the target frame: cover crops the overflow, contain letterboxes it against a background colour you pick, and stretch ignores the aspect ratio entirely.

What you get

Exact pixel entry with aspect-ratio lock
Percentage presets and one-click restore to original size
Cover / contain / stretch fitting with a background colour picker
Multi-step downscaling for sharp results
Change the output format at the same time

When to use the image resizer

Preparing images for a website

Serve roughly twice the CSS display width so the image stays sharp on high-density screens, and no more. A 4000 px photo in a 600 px column wastes about 95% of the bytes downloaded.

Meeting an upload requirement

Many forms specify exact pixel dimensions. Enter them directly, and choose Cover if the required aspect ratio differs from your image.

Making thumbnails

Batch-resize a folder to a consistent width so a gallery grid lines up neatly.

Shrinking screenshots for documentation

Retina screenshots are captured at 2× and look oversized when embedded. Resizing to 50% restores the intended size.

Common target sizes

Purpose	Dimensions	Fit mode
Full-width hero banner	1920 × 1080 px	Cover
In-article image	1200 px wide	Stretch (ratio locked)
Blog thumbnail	600 × 400 px	Cover
Product listing grid	800 × 800 px	Contain (white background)
Email header	600 px wide	Stretch (ratio locked)
Avatar / profile picture	400 × 400 px	Cover
Print at 300 DPI, 6 × 4 in	1800 × 1200 px	Cover

How it works

Naively scaling a large image down in one step skips most of the source pixels and produces aliasing: jagged diagonals and shimmering detail. This tool halves the image repeatedly until the next halving would overshoot the target, then does one final scale. Each halving averages four pixels into one, so no detail is simply discarded.

The three fit modes solve different problems. Stretch maps the source to the target box exactly, which distorts the image unless the ratios match. With the ratio lock on, they always do. Cover scales until the box is completely filled and crops the overflow from the centre. Contain scales until the whole image fits inside and fills the remainder with your chosen background colour.

Enlarging is a fundamentally different operation. Browsers interpolate between existing pixels, which can only ever produce a softer version of the original. There is no detail to recover. Beyond roughly 150% the softness becomes obvious. Recovering real detail requires a trained upscaling model running on a server, which this site does not do.

Common problems and how to fix them

The image looks squashed or stretched: The aspect ratio lock was off and the width and height you entered do not match the original proportions. Turn the lock on, or switch the fit mode to Cover so the overflow is cropped instead of squeezed.
Part of my image was cut off: That is Cover mode working as designed. It fills the frame and trims the rest from the centre. Use Contain if nothing may be lost.
The enlarged image is blurry: That is expected. Upscaling interpolates between pixels and cannot invent detail. Start from a larger original wherever possible.
There are coloured bands around my image: You are in Contain mode. Change the background colour to match your page, or switch to Cover to remove the bands.
My animated GIF lost its animation: Browser canvas APIs expose only the first frame. The result is a still image, and we would rather say so than hand back a broken file.

Frequently asked questions

Can I enlarge a small image?

You can, but upscaling cannot invent detail that was never captured. The result will look soft. Browsers use bilinear-style interpolation, not AI super-resolution. Enlarging beyond about 150% of the original rarely looks good.

What is the difference between cover and contain?

Cover scales the image until it fills the whole frame and crops whatever overflows, so no empty space remains. Contain scales until the entire image fits inside the frame, leaving bands of your chosen background colour. Use cover for banners and thumbnails, contain when nothing may be cut off.

Will resizing reduce the file size?

Almost always, and dramatically. File size scales roughly with pixel count, so halving the width and height typically cuts the file to a quarter or less.

What size should images be for a website?

Full-width hero images are usually 1600-2000 px wide, in-article images 800-1200 px, and thumbnails 300-600 px. Serve about twice the CSS display width to stay sharp on high-density screens. Serving a 4000 px image into a 600 px slot wastes most of the download.

Does it work with animated GIFs?

The first frame is resized and saved as a still image. The animation is not preserved. Browser canvas APIs cannot re-encode animated GIFs, and we would rather say so than silently return a broken file.

How do I resize an image to an exact file size instead of exact pixels?

Use the Image File Size Reducer, which binary-searches the encoder quality and downscales as needed until the file fits a byte budget you specify.

Will resizing reduce quality?

Downscaling discards pixels permanently, but the result looks sharp because it is displayed smaller. The visible quality loss comes from the re-encode, not the resize. Export as PNG for a lossless result.

Can I resize multiple images to the same size at once?

Yes. Drop up to 20 images, set the dimensions, then press "Process all images" and download the ZIP.

Resize an image to any dimensions

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