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AIFree · No sign-up · AI runs on your device

AI image upscaler.

Enlarge a photo to 2× or 4× its size with AI that sharpens detail instead of just stretching pixels. It runs in your browser, so your photo stays on your device.

Photo never leaves your device 2× or 4× Before and after preview No watermark
AI: an on-device upscaling model (about 5 MB, downloaded once and kept by your browser). Your photo is never uploaded.
Needs a reasonably modern computer — check your device.
Your photo is never uploaded to us. It’s upscaled right here in this browser tab. The first time, your browser downloads the AI model itself — your photo is never part of that download.
How it works

Upload, pick 2× or 4×, download a bigger, sharper photo

The upscaler runs a super-resolution AI model (Real-ESRGAN) inside your browser. It works through the photo square by square, sharpening edges and cleaning up blur and JPEG blockiness as it enlarges it.

01

Upload a photo

JPG, PNG or WebP from your device.

02

Choose 2× or 4×

Press Upscale — the first run downloads the model.

03

Compare and download

Drag the slider to see the difference, then save as JPG or PNG.

Why your photo never leaves your device

Most online upscalers upload your photo to a server with a graphics card. Altto runs the AI in your browser instead, using your own graphics card when the browser supports it.

  • Nothing is uploadedFamily photos and product shots stay on your device.
  • No watermarkEvery image you download is yours to use.
  • No account, no creditsUpscale as many photos as you like, free.
4×

larger, with sharper detail, all worked out on your own device.

Before you start

Will it run on my device?

Because the AI runs on your own device instead of on a server, your computer does the work — that’s what keeps your files private. Most computers from the last few years are fine, but a more powerful one is noticeably faster.

Your device:Checking…

Minimum

  • ComputerAny laptop or desktop from about the last 6 years
  • Memory (RAM)4 GB
  • BrowserThe latest Chrome, Edge, Firefox or Safari
  • DownloadAbout 5 MB the first time

Without graphics acceleration, a large photo can take a few minutes.

Recommended Fastest

  • ComputerA recent laptop or desktop
  • Memory (RAM)8 GB or more
  • BrowserChrome or Edge, which can use your graphics chip (WebGPU)
  • GraphicsAny built-in or separate graphics chip from the last few years

Recent phones can upscale smaller photos; 4× on a big photo needs a computer.

Tested on a mid-range PC with AMD Ryzen built-in graphics (no separate graphics card), in Chrome: A 640 × 420 photo enlarged 4× to 2560 × 1680 in 7 seconds.

FAQ

Frequently asked questions

Will it work on my computer or phone?
Most computers from the last few years run it fine. Because the AI runs on your own device, a more powerful computer is faster. See minimum and recommended specs, including a quick check of your device.
Is my photo uploaded?
No. The photo is upscaled inside this browser tab and is never sent to Altto or anyone else.
What gets downloaded?
Only the upscaling model, about 5 MB, the first time, plus the code that runs it. Your browser keeps them for next time.
How big can the photo be?
For 2× we work from up to 2048 pixels on the longest side, and for 4× up to 1024 pixels, so the result stays a size browsers can handle (up to about 4000 pixels). Bigger photos are reduced first, and we tell you when that happens.
How long does it take?
Usually a few seconds to half a minute on a computer whose browser can use the graphics card (recent Chrome and Edge). Without it, or on an older phone, a large photo can take a few minutes.
Will it fix a blurry photo?
It makes small or pixelated images bigger and crisper, but it can’t recover detail that was never captured — a badly out-of-focus photo will still look soft.
Is the result good enough to print?
Often, yes. Upscaling a phone photo 2× or 4× can take it from screen size to a decent print size. Check the preview at full size before you print.
Which AI model does it use?
Real-ESRGAN (general-x4v3) by Xintao Wang and colleagues, © 2021, used under the BSD 3-Clause licence. We converted it to run in web browsers and serve it from altto.co.uk. Licence.
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