Is my image uploaded to a server?

No. The image is decoded and redrawn on an HTML Canvas entirely in your browser. It never leaves your device, which makes the tool safe for private photos and unreleased assets.

Which output format should I choose?

Use JPEG for photographs to get small files with a quality slider, PNG when you need lossless output or transparency, and WebP for the best compression at a given quality where browser support allows.

Will resizing keep the aspect ratio?

When aspect-ratio lock is on, you set the width and the height is computed automatically so the image is not stretched. Turn the lock off to set both dimensions independently.

Why does upscaling look blurry?

Enlarging an image cannot add detail that was not captured, so the Canvas interpolates between existing pixels and the result softens. For best quality, resize down from a larger original rather than up from a small one.

What does the quality slider do?

For JPEG and WebP it controls the lossy compression level from 0.1 to 1. Lower values shrink the file but introduce artefacts; 0.8 to 0.9 is a good balance. PNG is lossless, so the slider does not apply.

Image Resizer (Local)

Resizing an image changes its pixel dimensions — useful for fitting an upload limit, generating thumbnails, or trimming a large photo down to a web-friendly size. This free tool does it on an HTML Canvas right in your browser, so your image is never uploaded.

How it works

The tool loads your file into an Image object to read its natural width and height. When you resize, it creates a Canvas at the target dimensions and calls drawImage to redraw the source at the new size. Browser Canvas scaling uses smoothed (bilinear-style) interpolation, with imageSmoothingQuality set to high, which produces clean downscaled results. The Canvas is then exported with toBlob in your chosen format and quality.

Tips and notes

Downscaling is where Canvas resizing shines; aim to start from an image larger than your target. For photographs, JPEG or WebP with a quality around 0.85 usually gives a much smaller file than PNG with no visible loss. Keep aspect ratio locked unless you specifically need a fixed frame, otherwise the image will look stretched. Because everything runs locally, large images use your device’s memory — very high-resolution sources may take a moment to process.