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Image Resizer

Resize an image to exact pixel dimensions in your browser, with the aspect ratio locked and a lossless PNG out.

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Quick answer

Image Resizer changes an image's pixel dimensions on an HTML5 canvas, in your browser. Type a new width or height and, with the aspect ratio locked (the default), the other side follows. You can also tap a preset: 1920, 1280 or 800. The result is saved as a lossless PNG, so resizing adds no compression artefacts. Your image is not uploaded and the original is left untouched.

  • 3presets: 1920, 1280, 800
  • PNGlossless output
  • Lockedaspect ratio by default
  • 0files uploaded

What the Image Resizer does

Sometimes an image is the wrong size in pixels: a 6000-pixel photo where 1200 would do, or an upload that must fit set dimensions. This tool redraws the image at the width and height you choose.

By default it keeps the proportions. Change the width and the height adjusts to match, so nothing looks stretched. Uncheck the aspect lock if you want to set both sides independently.

How it works

When you load an image, the tool fills in its current width and height and remembers the ratio between them. The presets and the aspect lock both work from that ratio, so a 16:9 photo stays 16:9 when you pick 1280.

Your chosen dimensions become a new canvas, and the image is drawn into it at that size with the browser's built-in smoothing. The canvas is saved as a PNG, a lossless format, so the pixel count is the only thing that changes.

Processing pipeline

  1. Step 1. Drop in an image. It is decoded locally.
  2. Step 2. The current width and height are filled in; the aspect ratio is locked by default.
  3. Step 3. Type a new width or height (the other follows), or tap a preset: 1920, 1280, or 800.
  4. Step 4. The image is redrawn at the new size on a canvas with the browser's smoothing.
  5. Step 5. Download the result as a lossless PNG.

Presets with the aspect ratio locked

1920 × 10801280 × 720800 × 45016:9locked
Example for a 16:9 image. Type one side and the other follows, so nothing stretches.

Privacy

Resizing runs on your device. The image is read from disk and redrawn in the page's memory, and the PNG is produced locally, so it is never uploaded.

The resized copy exists only until you download it or close the tab, and the tool asks for no login, so private photos are fine to use here.

Technical details

EngineHTML5 Canvas (browser-native)
ControlsWidth/height + aspect lock + presets (1920/1280/800)
OutputPNG (.png), lossless
ResamplingBrowser's built-in smoothing (bilinear)
Aspect ratioLocked by default; can unlock
UploadNone; resizing happens on your device

Standards and references

  • HTML Canvas API: drawImage scales the picture to the target size; imageSmoothingEnabled is on by default (bilinear), so pixels are interpolated rather than duplicated.
  • ISO/IEC 15948 (PNG): the lossless output format, so the resize itself adds no compression artefacts.

Accuracy and limits

Downscaling gives the best results: the tool drops pixels cleanly and the image usually looks good. It uses the browser's default bilinear smoothing, which suits typical reductions. Shrinking by a very large factor in one step can look a little soft next to a dedicated multi-step or bicubic resampler.

Upscaling cannot create detail. If you set dimensions larger than the original, the tool interpolates new pixels, so the image gets bigger but not sharper and may look soft or blocky. Enlarging suits small bumps in size, not rescuing a tiny image.

With the aspect lock on, the opposite dimension is computed for you so nothing distorts. Turn it off only if you mean to stretch the image to exact, non-proportional dimensions.

The output is a lossless PNG, so resizing adds no JPEG-style artefacts. A photo saved as PNG can be larger than the same photo as JPEG, so if file size matters, compress the resized image afterwards.

Shrinking vs enlarging

Downscaledrops pixels cleanlyUpscalebigger, not sharper
Downscaling drops pixels cleanly. Upscaling makes the image bigger but not sharper.

Real-world uses

Fit upload requirements

Hit a site's exact pixel dimensions for an avatar, banner, or product image.

Lighten big photos

Bring a multi-thousand-pixel photo down to a web-friendly 1280 or 800.

Consistent sizing

Make a set of images share the same width for a gallery or grid.

Thumbnails

Generate a smaller version for previews or listings.

When it fits, and when it doesn't

Good for

  • Setting exact pixel width/height
  • Downscaling large photos
  • Keeping proportions with the aspect lock
  • A lossless resized copy

Not the best choice for

  • Adding real detail by enlarging
  • Making the smallest possible file (PNG is larger)
  • Cropping to a region (this scales, not crops)
  • Changing only quality, not size

To cut file size, compress the resized image. To keep a region at full size instead of scaling, use an image cropper.

Tips and tricks

What we would do

Frequently asked questions

Does resizing keep the proportions?
Yes, by default. With Keep aspect ratio on, changing the width sets the height automatically (and vice versa) so the image is not stretched. Uncheck it to set both sides independently.
What format does it save?
A lossless PNG, regardless of the input format. Because PNG is lossless, the resize itself adds no compression artefacts.
Can I make an image bigger?
You can enter larger dimensions, but enlarging interpolates new pixels: the image gets bigger, not sharper, and may look soft. Resizing down looks far better than resizing up.
Will downscaling look blurry?
For normal reductions, no. The browser smooths as it scales. Shrinking by a very large factor in one go can look slightly soft compared with a dedicated resampler.
Are the presets the width or the height?
The presets (1920, 1280, 800) set the width, and with the aspect lock on the height is computed to match. They are handy targets for common screen and web sizes.
Are my images uploaded?
No. Resizing happens on an HTML5 canvas in your browser. Nothing is sent to a server, and refreshing clears it from memory.
Why is the PNG bigger than my original JPG?
PNG is lossless, so a photo saved as PNG is often larger than the same photo as JPEG. If you want a smaller file, compress the resized PNG or convert it to JPG or WebP.
Can I crop instead of scale?
No. This tool scales the whole image to new dimensions. To keep part of the image at full size, use an image cropper.
Is my original changed?
No. A new resized PNG is created and your original file is left as it was.
Does it work on a phone?
Yes, in any modern mobile browser. Very large images use more memory while resizing.

References

Written from the tool's canvas scaling and PNG export code, including the limit that enlarging an image cannot add detail.

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Back to the Image Resizer

Your file is processed on this device and never uploaded, and there's no account to create.

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