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Z Image Tools

Image Resizer — Resize by Pixels, Percent & Aspect Ratio

Resize images by width, height, percentage, or exact dimensions. Aspect ratio lock. Files never upload.

Free No signup Client-side Privacy friendly Updated

Drop an image here, or

Max 25 MB. Files never leave your browser.

Source

× · ·

Output

Processing…

× · ·

How to use

  1. 1 Drop an image.
  2. 2 Pick resize mode — by width, by height, by percentage, or exact both.
  3. 3 Keep aspect ratio on for proportional resize.
  4. 4 Download the resized result.

Why use this tool

  • Four resize modes — covers every common workflow.
  • Aspect-lock prevents accidental distortion.
  • Choose output format separately from resize.
  • Pure client-side — no upload, no signup, no watermark.

Frequently asked questions

What is the maximum image size?

25 MB input, 10000×10000 px output. Larger inputs are blocked to prevent browser OOM on mobile.

Will it upscale?

Yes — percent mode supports up to 400%, and exact width/height can exceed source dimensions. Upscaling results in blurry output since there is no detail to invent.

Why is the output sometimes blurry after resize?

Browser canvas uses bilinear filtering by default. For very large downscales, consider doing it in two steps, or use a dedicated tool with Lanczos filtering.

What is Image Resizer?

An Image Resizer is a tool that changes the dimensions of an image by width, height, percentage, or exact pixel dimensions. It offers an aspect ratio lock to keep proportions intact while scaling. The tool runs entirely in the browser using client-side processing, so files are never uploaded to a server, making it suitable for quickly preparing images at a target size.

Features

Four resize modes

Resize by target width, target height, a percentage of the original (1-400%), or exact width and height together with aspect lock disabled.

Aspect ratio lock

When resizing by width or height alone, aspect lock computes the matching dimension from the source ratio to prevent stretching or squashing.

Independent output format

Keep the original format, or convert to JPEG, WebP, or PNG regardless of resize mode; JPEG output flattens transparency onto a white background.

Client-side only, 25 MB cap

All decoding and re-encoding runs in the browser via the Canvas API — no upload to a server. Input files over 25 MB are rejected before processing.

Example

Input

screenshot.png — 2560x1440, 3.1 MB, mode=width, width=1280, aspectLock=true, output=JPG, quality=85

Output

screenshot.jpg — 1280x720, ~210 KB, transparent/alpha areas flattened to white background, bilinear-resampled (canvas imageSmoothingQuality=high)

Common use cases

  1. 1

    Shrink photos for web upload

    Resize a camera photo down to a specific width (e.g. 1200px) before attaching it to a blog post or product listing, keeping file size and page load time down.

  2. 2

    Prepare a fixed-size thumbnail

    Use 'both' mode without aspect lock to force an image to an exact width and height needed by a template or CMS field, such as a 300x300 avatar slot.

  3. 3

    Batch down-scale a set of screenshots

    Use percent mode to scale a large screenshot to 50% for documentation, then export as WebP or JPEG to cut file size further.

Summary

Image Resizer changes an image's pixel dimensions by width, height, percentage (up to 400%), or exact width+height, with an optional aspect-ratio lock. It decodes the file with createImageBitmap, draws it onto a Canvas/OffscreenCanvas at the target size, and re-encodes with toBlob/convertToBlob to PNG, JPEG, or WebP (JPEG/WebP quality adjustable 10-100%). Processing happens entirely in the browser — the image is never uploaded to a server.

Category
Creator
Pricing
Free
Privacy
Browser-based
Signup
Not required

References

Privacy

Your data never leaves your browser unless explicitly stated. Image Resizer runs entirely client-side — no server upload, no logging, no tracking of your input.

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