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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.

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At a glance

AI image upscaler: quick facts

Enlarge a photo 2× or 4× with AI that runs on your device.

Updated

Price
Free. No sign-up, no watermark.
Output
PNG or JPG, up to about 4,000 pixels across.
Input limits
Up to 2,048px for 2×, 1,024px for 4× (bigger photos are reduced first).
AI model
Real-ESRGAN (general-x4v3), about 5 MB, downloaded once from altto.co.uk.
Speed
Seconds to half a minute on a recent computer; longer on older phones.
Privacy
Your photo is upscaled in your browser and never uploaded.
How it works

How to upscale a photo with AI

Choose 2× or 4×, add a photo, and the AI redraws it at the larger size, sharpening edges and detail rather than just stretching pixels. Save it as a smaller JPG or a lossless PNG.

  1. 01

    Choose a photo

    JPG, PNG or WebP from your device.

  2. 02

    Choose 2× or 4×

    Press Upscale — the first run downloads the model.

  3. 03

    Compare and download

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

Tips

Tips for the best upscaled photos

AI upscaling works best when it has good material to start from, and when you check the result before you use it.

  • Start from the best copy you haveThe AI can only build on what’s in the photo. An original from your camera roll upscales far better than a copy saved from social media or a messaging app, which has usually been compressed on the way.
  • Choose 2× unless you need 4×For 4×, photos are first reduced to at most 1,024 pixels on their longest side, against 2,048 for 2×. If your photo is already fairly large, 2× often keeps more of its real detail.
  • JPG to share, PNG to editJPG gives a much smaller file that’s fine for sharing and printing. Choose PNG if you’ll keep editing the picture, as it saves every pixel exactly.
  • Check faces and text up closeUpscaling can smooth skin and invent tiny details that were never there. Zoom in on faces, writing and fine patterns before you use the result, especially for anything official.

Like every Altto tool, this runs on your device — nothing you add is uploaded. How Altto works

16×

as many pixels come out of a 4× upscale: four times the width multiplied by four times the height.

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.
How big can I print the result?
For a sharp print, divide the width in pixels by 300 to get the width in inches. A 4× upscale of a 1,000-pixel-wide photo is 4,000 pixels, about 34 cm (13 inches) wide at 300 pixels per inch, and larger still for a poster viewed from a distance.
Can it upscale drawings, logos or screenshots?
It’s made for photos, so drawings, logos and screenshots with flat colours and sharp lines can come out slightly painterly. For a logo, a vector version (such as an SVG) from whoever designed it will always print sharper than any upscaled copy.
Why is 4× limited to smaller photos?
Every pixel is worked out on your own device, and a 4× result has 16 times as many pixels as the photo going in. Limiting the size of the input keeps the result to a size your browser can handle without running out of memory.
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