Free Online Image Resizer — No Upload
Your photo is decoded and edited in this tab. It stays local, including whatever its metadata says about where it was taken.
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How it works
Lanczos, and why the browser's default is not enough
Drawing an image into a smaller canvas with drawImage uses the browser's built-in scaler, which samples too few source pixels when the reduction ratio is large. Taking a 4000-pixel-wide photo down to 400 that way means most source pixels contribute nothing at all, so fine detail aliases into moiré and diagonal edges break up into stairsteps. This resizes with pica, which applies a Lanczos windowed-sinc kernel across the full source neighbourhood — every input pixel is weighted into the output, so text stays readable and hairlines survive.
- Lanczos kernel
- A windowed sinc filter applied over the whole source neighbourhood. Slightly sharper than bilinear or bicubic, and visibly cleaner at big reductions.
- Aspect ratio lock
- On by default. Typing a width fills in the matching height. Unlock it only when you actually intend to stretch the picture.
- Pixels or percentage
- Absolute dimensions when a spec demands them, a percentage when you just want half the size of whatever you dropped in.
- Upscaling
- Available, but resampling invents no detail. Enlarging a 400px image to 1600px produces a smooth, soft 1600px image, not a sharper one.
- Density
- The output carries pixel dimensions, which is what browsers and CSS use. A DPI number only affects how print software chooses a default physical size.
How to use it
How to resize an image online
- 01
Drop the image in
The original dimensions are read from the file and shown before you start.
- 02
Type a width, height or percentage
With the ratio locked, one number is enough — the other follows and nothing gets stretched.
- 03
Export at the size you set
Keep the original format or switch it, then download the resized copy.
Where it earns its keep
Where an exact image size is required
- Hitting the pixel dimensions a marketplace or job board demands for an upload.
- Making @1x and @2x versions of an asset from one high-resolution source.
- Cutting a camera original down to something reasonable for a web page.
- Fitting an avatar or header into a platform's stated crop box before uploading.
Questions
Image Resizer, answered
Can it make a small image sharp at a larger size?
No. Resampling redistributes the detail that already exists; it cannot create detail that was never captured. An upscale will be smooth rather than blocky, but it will not be sharper than the source. Machine-learning upscalers are a different technique and are not what this does.
Is my image uploaded to be resized?
No. The file is decoded, resampled and re-encoded in this browser tab. Open the network inspector while you resize — nothing carrying the image is sent.
Why does the result look better than other resizers?
Because most of them hand the work to canvas drawImage. At large reduction ratios that scaler skips source pixels and aliases; the Lanczos filter here weights the whole neighbourhood, which is what keeps small text and fine lines intact.
Is there a maximum image size?
On iOS and Safari, yes. The browser caps total canvas area at roughly 16.7 megapixels, and older devices at 4096×4096, so very large images are clamped to fit. Desktop Chrome and Firefox allow considerably more.