Image Resizer
Resize images to exact dimensions. Includes presets for Instagram, Twitter, and Facebook. Sharp results every time.
Drop your image here
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How it works
This resamples an image to new dimensions in your browser. Type a width and height, or pick one of the presets, and download the result. Nothing is uploaded.
Resampling uses pica at Lanczos3 with a light unsharp pass, rather than a plain canvas drawImage. The difference shows when you shrink a lot: a naive canvas downscale samples too few source pixels and leaves detailed areas aliased and crunchy, while Lanczos averages across the whole region it is collapsing. On a 4000px photo going to 400px that gap is obvious.
More detail
Presets and aspect ratio
The presets cover the sizes people actually need: profile squares at 400 and 150, HD and Full HD, 4K, and the current Twitter, Instagram and Facebook cover dimensions. Custom lets you type anything.
Aspect ratio is locked by default, so typing a width fills in the matching height. Turn the lock off and the image is stretched to whatever dimensions you give, distortion included - occasionally what you want, usually not.
Presets deliberately ignore the lock and set both dimensions. Picking a square preset for a landscape photo will squash it. If you want a square crop rather than a squashed one, crop before you resize.
Things worth knowing
Enlarging does not add detail. Scaling a 400px image to 1600px gives you a 1600px image with 400px worth of information in it, and interpolation that makes it look soft. If you need more resolution, you need a better source.
Metadata does not survive. The image is decoded to pixels and re-encoded, so EXIF, GPS and colour profiles are dropped.
Alpha survives into PNG and WebP. Resizing a transparent PNG and saving as JPEG will composite the transparency onto white, because JPEG has no alpha channel.
Limits are 50 MB per file, 100 megapixels, and 16384 pixels per side, that last being the browser's canvas ceiling.
Questions
Does the file leave my machine?
No. Resizing happens on a canvas in your browser and the file never leaves your machine.
Will resizing make my image blurry?
Shrinking should not, because the resampler averages properly rather than dropping pixels. Enlarging will, unavoidably: there is no extra detail to invent, so interpolation smooths what is there.
Does it keep the aspect ratio?
By default yes, and changing one dimension updates the other to match. With the lock off, or with a preset whose shape differs from your image, the result is stretched to those exact dimensions rather than fitted inside them.
Why is my resized file bigger than the original?
Usually because the output format changed, most often to PNG. A photograph stored as PNG is far larger than the same photograph as JPEG or WebP, regardless of dimensions. Pick a lossy format for photographic content.