Image Resizer
Select an image, set a new width or height, and download the resized result. Everything happens on your device — nothing is uploaded or stored anywhere.
How Image Resizer Works
This tool changes an image's pixel dimensions using the HTML5 Canvas API, drawing your original photo onto a canvas at a new width and height and exporting it as a PNG, JPG, or WebP file. Everything runs locally in your browser, so nothing is uploaded to a server.
Formula & Method
When "Maintain aspect ratio" is checked, changing the width automatically recalculates the height as new height = round(new width ÷ original aspect ratio), where the original aspect ratio is original width ÷ original height -- and the same happens in reverse when you change the height. This keeps the image from looking stretched or squashed. Unchecking the box lets you set width and height independently, which can distort the image if the new ratio doesn't match the original.
Worked Example
For a 1920×1080 original with aspect ratio locked, typing 800 into the Width field gives an aspect ratio of 1920 ÷ 1080 = 1.7778, so the new height is calculated as round(800 ÷ 1.7778) = 450 -- producing an 800×450 image that keeps the same 16:9 proportions as the original.
Frequently Asked Questions
- Will resizing an image reduce its file size?
- Usually yes, since fewer pixels generally means less data to store, but file size also depends on the output format and image content. Use the Image Compressor afterward if you want more direct control over file size via a quality setting.
- What happens if I uncheck "Maintain aspect ratio"?
- You can then set width and height completely independently. This is useful for fitting an exact box size, but if the new ratio differs from the original, the image will appear stretched or squashed.
- Can I enlarge a small image with this tool?
- Yes -- the width and height fields allow values up to twice the image's original largest dimension. Keep in mind that enlarging a photo beyond its original size doesn't add real detail, so it may look softer or blurrier than a native high-resolution image.
- Which output format should I choose?
- PNG preserves transparency and sharp edges (good for graphics/screenshots), JPG is compact for photos but has no transparency, and WebP typically gives the smallest file size for photos while still supporting transparency.