About Upscale an Image 4x
This page opens at x4. A 500 by 400 px picture becomes 2000 by 1600 px. Because the result is limited to 4096 px, the input can be at most 1024 px on its long side. It is free, needs no sign-up and runs in your browser, so nothing you enter is uploaded.
x4 suits thumbnails, small icons and old low-resolution scans. Look closely at faces and text afterwards, because the model has more to invent at this scale.
How to use Upscale an Image 4x
- Choose the scale: x2 or x4. Each has its own model of about 22 MB.
- Press Download model and confirm. The model comes from Hugging Face and your browser may keep it for next time.
- Add a picture by dropping it, tapping the box, pasting it or using the phone camera.
- Check the size note. If the picture is larger than the limit for that scale, it is shrunk first and a warning says so.
- Press Upscale. A progress bar shows the tile being worked on. Press Stop to cancel.
- Compare before and after with the slider on a phone or side by side on a large screen, then press PNG.
Features
- Swin2SR at x2 and x4, each about 22 MB.
- Tiled inference in 128 px tiles with a 16 px overlap that is blended, so big images do not run out of memory.
- Runs in a worker, with a progress bar and a Stop button.
- An honest size limit: the result stays within 4096 px on its long side, and the tool says when it shrank the input.
- Before and after compare, as a slider on phones and side by side at large widths.
- Download as a PNG at the upscaled size.
- Input by drop, file choice, paste or phone camera.
- Nothing is uploaded: only the model is downloaded.
Privacy: how it works
- Pictures are processed in your browser and are never uploaded to Ulkaa or to anyone else.
- The only download is the Swin2SR model (about 22 MB per scale) from Hugging Face. That request does not contain your pictures.
Tips
- Start from the best source you have. Upscaling a heavily compressed JPG also enlarges its blocky artefacts.
- Use x2 first. It is about four times cheaper than x4 on the same picture.
- Crop the part you care about before you upscale, to spend the memory on it.
- Keep the original. The result is a new PNG and the tool never changes your file.
Frequently asked questions
Is it really free?
Yes. There is no price, no trial and no credit card. Ulkaa Tool does the work with your own device, so there is no server bill to pass on to you.
Do I need an account?
No. There is no sign-up and no login. Open the page and use it. An Ulkaa account is not needed for anything on this tool.
Does it run in my browser?
Yes. Your pictures are processed by code running in your browser tab, on your own device.
Is my data uploaded?
No. Your pictures are never sent to Ulkaa or to anyone else. You can check this yourself by watching the Network tab in your browser developer tools while you use the tool.
Why is the x4 input limit lower?
The result may not pass 4096 px on its long side, and 4096 divided by 4 is 1024.
Is x4 better than running x2 twice?
Not necessarily. A single x4 pass is one model run per tile, while two x2 passes double the work and can compound artefacts.