Image Upscaler

About Image Upscaler

Make a picture bigger without it turning into a soft, smeared version of itself. Upload an image, pick 2×, 3×, 4× or an exact width, and download the result. Nothing is uploaded — the whole thing runs on your own device.

What this actually does — and what it does not

This matters, so it is worth being straight about it.

When your browser, or a photo app, enlarges a picture, it usually uses a simple average of the nearest few pixels. That is fast, and it looks soft: edges lose their bite and fine text goes mushy.

This tool does two things instead.

It uses Lanczos-3, not bilinear. Your browser takes 2×2 pixels and smears them. Lanczos weighs a 6×6 window with a curve that keeps edges roughly where they were.

And then it checks its own work. Having enlarged the picture, the tool *shrinks its own result back down* to the original size and compares it with the file you gave it. Wherever the two disagree, that difference is enlarged and added back in. Two rounds of this pull back detail the first pass had smeared. This is a real super-resolution technique, and it is why the result beats a plain Lanczos resize rather than merely matching it.

What it still does not do is invent detail. There are AI models that will guess at eyelashes and brick texture that were never in the file, and sometimes they guess well. This is not one of those. Everything here recovers what the *resampling* lost; nothing here makes up what the *file* never had. If your source is a 200-pixel thumbnail saved at low quality, you will get a bigger, cleaner version of a 200-pixel thumbnail, not a photograph.

Features

• Lanczos-3 resampling — the filter professional image software uses, not the browser's soft default
• Back-projection, which corrects the enlargement against your original file
• 2×, 3×, 4×, 6× or an exact pixel width with the shape kept
• A full-size close-up of the result next to what a plain resize would have given, so you can see the difference without downloading anything
• Sharpen slider — an unsharp mask at a radius matched to how far you enlarged
• Smooth out noise slider — applied *before* the enlargement, where grain and JPEG blocking actually are
• Save as PNG, JPG or WebP, with a quality control for the two lossy ones
• Transparency is kept in PNG and WebP, with no dark fringe at the edges of a cut-out
• Before and after side by side, with the real pixel size of each
• 100% in your browser — nothing uploaded, no sign-up, no watermark

Getting the best result

• Start with the biggest original you have. Enlarging the 800-pixel copy of a photo you also have at 3000 pixels is throwing quality away for no reason.
• Use Smooth out noise on grainy or heavily compressed pictures, and leave it at zero on clean ones. It runs before the enlargement, so it removes noise instead of spreading it around.
• Do not overdo the sharpening. The self-correcting pass has already put most of the edge back, so the slider only has to finish the job — 20 to 30 suits most photos, and past about 50 you start to see pale halos along strong edges. Sharpening is the one setting that can make a result measurably worse than leaving it alone.
• 2× looks better than 4×. Every step further from the original is more guessing. If 2× is enough, use 2×.
• PNG for logos, line art and screenshots. JPG for photographs. WebP gives smaller files than either, and every current browser reads it.

What people use it for

• Printing a photo that is fine on screen but too small on paper
• Product photos that a marketplace insists must be at least 1000 or 1600 pixels
• Old scans and phone photos from a camera that was not very good
• Logos and screenshots that need to be sharp on a big display
• Game art and pixel art enlarged for a poster or a print

Limits

Every stage holds the picture as 32-bit numbers, which is what makes the maths come out right — and it costs sixteen bytes a pixel. So anything beyond roughly 20 megapixels (about 5500 × 3600), or 10000 pixels on a side, is reduced to fit, and you are told on screen what size you actually got.

A 4× enlargement of a modern 12-megapixel phone photo would be 192 megapixels, so this comes up more often than you would think — 2× is usually the sensible answer there.

The self-correcting pass is the expensive part, so it runs twice up to about 4 megapixels, once up to 12, and is skipped above that. The status line tells you how many passes it did.

Related tools

• Image Resizer — make a picture smaller, or to an exact size
• Image Compressor — reduce the file size of the result
• Compress Image to a Size — hit an exact file-size limit
• Change Image DPI — set the print resolution before printing
• Crop Image — trim before you enlarge, so you are not enlarging what you will throw away

How to use it

• Upload an image — click the box or drop a file onto it
• Choose how much bigger you want it, or pick *Exact width…* and type a number
• Set Sharpen — the default of 25 is right for most pictures; raise it only if the result still looks soft
• Turn up Smooth out noise only if the original is grainy or heavily compressed
• Choose the format you want to save as
• Press Enlarge the image and wait a moment — a big enlargement takes a few seconds
• Press Download, and open the file to judge it at its real size