Image Resizer
Resize an image locally by entering an optional target width; height is calculated from the original aspect ratio. The browser decodes the file, draws it to a canvas at the new dimensions, and downloads a newly encoded result. No image pixels are uploaded.
Runs locally — files stay on your deviceCan an image be resized without distortion?
Yes. Change one dimension and preserve the original aspect ratio so width and height scale together.
Pixel dimensions and resampling
Resizing changes the number of pixels used to represent an image. Keeping the same width-to-height ratio avoids geometric distortion. Downscaling discards detail; upscaling creates additional pixels by interpolation but cannot recover detail absent from the source.
How it works
The implementation decodes the selected file, calculates a width ratio, draws the bitmap onto a canvas, and exports a new file. A 25 MB input limit and decoded-dimension safeguards reduce browser memory risk.
When to use it
- Prepare a smaller web image.
- Match an asset to a layout width.
- Reduce pixel dimensions before compression.
When not to use it
- Do not upscale a tiny source expecting new detail.
- Do not use resizing when you need to remove outer content; crop instead.
- Do not assume pixel dimensions alone determine file size.
Worked examples
Half-width photo
- Input
2400 × 1600 image; width 1200- Expected output
1200 × 800 image
The aspect ratio remains 3:2.
Avatar source
- Input
800 × 800 image; width 256- Expected output
256 × 256 image
A square remains square.
No width entered
- Input
1600 × 900 image- Expected output
1600 × 900 re-encoded image
Dimensions remain unchanged.
Common mistakes
Changing only one dimension mentally
An arbitrary second dimension can stretch the subject. Correction: Preserve the original ratio unless distortion is intended.
Confusing dimensions and bytes
Format, content, and quality also control file size. Correction: Use compression after choosing dimensions.
Repeated lossy processing
Repeated JPEG encoding can accumulate artifacts. Correction: Resize from the best available source.
Related operations and differences
Crop Image
Cropping removes part of the frame; resizing changes the pixel grid for the whole frame.
Image Compressor
Compression targets byte size and quality rather than dimensions.
Limitations and privacy
- Very large decoded images can exceed browser memory.
- Upscaling cannot recreate missing detail.
- Export format support depends on the browser.
Processing uses browser APIs on this device; the entered content is not sent to the Toolbox server.
Frequently asked questions
Does resizing reduce quality?
Downscaling removes detail; upscaling interpolates pixels. The visible impact depends on the ratio and source.
Is aspect ratio preserved?
Yes, when a target width is supplied the height follows the original ratio.
Why can a smaller image still be a large file?
Encoding format, quality, transparency, and image complexity also affect bytes.
What happens to metadata?
Canvas export creates a new image and commonly omits source metadata.