Upscale image
To upscale an image is to turn a few pixels into more without jagged or mushy edges. Choose a photo, pick a factor, save: the Lanczos method runs in your browser and the image is never uploaded. A magnifier shows right away how much better it looks than simple enlarging.
Source: Wikipedia – Lanczos resampling. Updated: .
How it is calculated
In short: when you enlarge an image, new pixels have to be invented. The tool calculates them with the Lanczos method (Lanczos-3): each new pixel is a weighted average of the nearest 6 × 6 original pixels, with weights that follow a sinc curve. The result has clean edges without stair-stepping and looks sharper than the browser’s simple enlargement.
How it works
- Drop an image, choose one or paste it with Ctrl + V.
- Pick the factor (1.5×, 2×, 3× or 4×). The target size in pixels appears below.
- The magnifier shows the image centre three ways: as single pixels, with the smooth browser method and with Lanczos.
- Choose a format and click “Upscale and save image”.
Honest limits
- This is not AI: no detail is invented. A tiny, heavily compressed photo stays soft; it is only enlarged cleanly, without amplifying stair-steps and block edges.
- For printing, the final pixel count is what matters: use the print size calculator to see how large the result can be printed at 300 dpi.
- The size is capped at your browser’s limit (50 megapixels, 16.7 megapixels on iPhone and iPad). If it is exceeded, the factor is shortened automatically.
- Transparent areas are kept; edges are calculated without a dark fringe.
Privacy
The image is processed only in your browser and is not uploaded.
Frequently asked questions
How can I enlarge an image without losing quality?
Completely lossless is not possible because pixels are added that did not exist before. With the Lanczos method, edges stay clear and free of stair-steps. Choose the image, set the factor, save.
Is this AI upscaling?
No. The tool works purely mathematically and does not invent detail. The image stays faithful to the original, with no artificial faces or textures.
How large can the result be?
Up to 50 megapixels, up to 16.7 megapixels on iPhone and iPad. If the chosen factor is too large, the tool shortens it automatically and tells you.
What does the magnifier show?
A small crop of the image centre in three versions: pixels simply enlarged, with the smooth browser method and with Lanczos. You see the difference before saving.
Is my image uploaded?
No. The enlargement runs entirely in your browser; the image never leaves your device.
Which format should I choose?
PNG is lossless but large. JPG is smaller for photos, WebP is a good compromise. “Like original” keeps JPG for photos and PNG for graphics.
Sources and legal basis
- Wikipedia – Lanczos resampling
- Duchon, C. E. (1979): Lanczos Filtering in One and Two Dimensions, Journal of Applied Meteorology
- MDN – CanvasRenderingContext2D.imageSmoothingQuality
- MDN – ImageData: pixel data of a canvas (RGBA, 8 bit)
- ITU-T T.81 / ISO/IEC 10918-1 – JPEG
- W3C – Portable Network Graphics (PNG) Specification
- Google for Developers – An image format for the Web (WebP)
- AOMedia – AV1 Image File Format (AVIF)
- MDN – Image file type and format guide
- MDN – HTMLCanvasElement.toBlob()
- Open-source licenses of the libraries used (MIT, LGPL-3.0)
As of: · Editorial policy
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