Images
Resize an image
Resizing happens on a canvas in this tab, so a private photo never travels over a network. Lock the aspect ratio and typing one dimension fills in the other.
Drop an image here, or click to browse — nothing is uploaded.
How to use it
- Drop an image or click to choose one.
- Type a width — the height follows if the lock is on.
- Pick a percentage button for a quick halving or quartering.
- Press Resize, then Download.
Why a 2× image is not waste
Phone and laptop screens pack two or three physical pixels into every CSS pixel. A 400-pixel-wide image placed in a 400-pixel slot is therefore rendered at 800 or 1200 device pixels and will look soft. Serving a 2× asset and letting the browser downscale is the standard fix. The cost is up to four times the bytes, which is why responsive images with a srcset exist rather than one large file for everybody.
Shrinking in one step is fine; enlarging is not
Downscaling works because the browser samples the source densely enough to average correctly. Upscaling cannot invent detail — it interpolates between existing pixels, so a 200-pixel image enlarged to 800 stays soft regardless of algorithm. If you need a larger version, obtain a larger original. No setting recovers information that was never captured.
Sizing for retina screens and email
A CSS width of 400 px on a 2× display needs a 800 px source; ship the 400 and it looks soft to anyone on a modern phone, which is most people. The usual compromise is to serve the 800 px file at 400 px via srcset, letting the browser pick — one file for both, no JavaScript.
Email is the opposite discipline: Outlook's rendering engine ignores most responsive CSS, so a 600 px wide table is still the safe maximum, and images above that get scaled down badly or overflow on narrow clients.
Frequently asked questions
Does resizing change the file size?
Yes, usually substantially — pixel count scales with the square of the linear dimension, so halving the width cuts the pixels to a quarter. JPEG quality adds a second lever on top of that.
Should I choose JPEG, PNG or WebP?
JPEG for photographs, PNG when you need transparency or lossless edges, WebP when you want both at a smaller size for the web. WebP support is universal in current browsers.
Why did my transparent PNG get a white background?
JPEG has no alpha channel. If you need transparency, switch the output format to PNG or WebP before resizing.
Is there a file size limit?
Only your device's memory. A 40-megapixel photo is fine; extremely large images may hit canvas size limits in older browsers.
Will resizing up improve a small image?
No. Enlarging invents pixels. A 400 px photo stretched to 1200 px is softer than the original, and no resampling filter changes that.
Does resizing change the file size predictably?
Roughly with the square of the scale for uncompressed data, but encoding does not follow a straight line. Halving the dimensions usually cuts a JPEG to about a third, not a quarter.