Image Resizer
Resize images by width or height with an aspect-ratio lock — fully local in your browser.
Written by Golam Rabbani, Founder & Lead Engineer
How to use this image resizer
- Choose an image file (PNG, JPG, WebP, or GIF) from your device.
- Enter the target width or height — keep "Lock aspect ratio" on to scale proportionally.
- Press "Resize Image" to render the result on a canvas in your browser.
- Preview the output and click "Download" to save the resized file locally.
- Use "Reset" to clear everything and start over with a different image.
About this image resizer
An image resizer changes the pixel dimensions of a picture so it fits a specific layout, file-size budget, or upload limit. This tool decodes your file with the browser's native createImageBitmap API, draws it onto an off-screen canvas at the dimensions you choose, and re-encodes the result with canvas.toBlob — the same path Chrome and Safari use for their own image pipelines.
Crucially, everything happens locally: your image never leaves the browser, never uploads to a server, and is not stored anywhere. Once you close the tab, all references are released and the in-memory bitmap is garbage-collected. That makes the tool safe for product photos, ID scans, screenshots, or any picture you would not want to hand to a third party.
As a worked example, a 4032 × 3024 px iPhone photo (about 3.4 MB JPEG) resized to 1200 × 900 px typically lands around 220 KB without visible quality loss — small enough to attach to an email or upload to a CMS that caps assets at 500 KB. Aspect-ratio lock keeps the photo from squishing when you only specify one side.
The maximum supported dimension is 8000 px on either side, which covers virtually every modern monitor, print layout, and social-media upload. For larger pictures, resize twice or use a desktop editor.
FAQ
- Are my images uploaded anywhere?
- No. The resizer runs entirely in your browser using the HTML canvas API. Your file is read from disk, decoded in memory, redrawn, and re-encoded locally — no network request is ever made with your image data.
- Will resizing reduce file size as well as dimensions?
- Usually yes. Smaller pixel dimensions mean fewer pixels to encode, so JPEG and WebP outputs shrink dramatically. PNG savings depend on how compressible the new image is, but they are still typically significant.
- Does the tool preserve the original format?
- Yes. The output uses the same MIME type as the input where possible, so a PNG goes in and a PNG comes out. If you need a different format, run the result through one of the dedicated converters (PNG to JPG, PNG to WebP, etc.).
- Why is there a maximum size of 8000 pixels?
- Canvas operations above ~8K on a side can hit per-browser memory limits and crash the tab on lower-end devices. Capping the max keeps the tool reliable across phones, tablets, and laptops.
- Will resizing improve the quality of a small image?
- No. Upscaling can only invent pixels by interpolation, which softens the result. For best quality, resize down from the largest source you have rather than up from a small one.