Upscale an Image to 4K for Free
Pick 4K and the AI enlarges your photo until its long side reaches about 3840 px. Free, no sign-up, processed on your device.
Next: put this photo on a new background with the background changer, restyle a room with interior design AI, or turn a product shot into a studio scene with phone photo to studio. First result free.
The AI model (about 5 MB) downloads once the first time you upscale. 8× = AI 4× plus a smooth 2× resize. Maximum result about 16 megapixels.
Real result: bicubic vs AI upscaling
The same 400 px photo enlarged 4×. Left: standard bicubic resize. Right: Real-ESRGAN in this tool. Drag the handle.
Bicubic 4×AI 4×To upscale an image to 4K, upload it here and choose "4K": the Real-ESRGAN AI model enlarges it 4× and the result is fitted so the long side is about 3840 px (UHD width). It is free, runs in your browser without uploading the photo, and has no watermark. A 960 × 540 source becomes 3840 × 2160.
Facts checked October 10, 2026.
What you get
| Price | Free. No credits, no sign-up, no daily limit. |
|---|---|
| Watermark | None. |
| Privacy | Runs in your browser; the image is never uploaded. |
| Model | Real-ESRGAN general-x4v3 (open source, BSD-3) via onnxruntime-web; WebGPU when available, otherwise WebAssembly. |
| Scales | 2× and 4× by the AI; 8× = AI 4× + smooth 2×; 4K = long side about 3840 px. |
| Limits | Result up to about 16 MP; JPG / PNG / WebP in, PNG out; transparency becomes white. |
| Not the right tool for | Recovering faces or text that are unreadable in the source — the AI adds plausible detail, not the original. |
How it works
1. Choose an image
JPG, PNG or WebP. It stays on your device — the page reads it locally.
2. Pick 2×, 4×, 8× or 4K
The AI processes the image in small tiles and blends them, so even large photos upscale without seams.
3. Compare and download
Drag the slider to compare with a plain resize, then download the PNG.
FAQ
What size is 4K?
4K UHD is 3840 × 2160 pixels. This tool makes the long side of your image about 3840 px and keeps the original aspect ratio.
Can a tiny image become a sharp 4K image?
The AI adds plausible detail, but it can't recover information that isn't there. Sources of at least 800–1000 px wide give the cleanest 4K results.
Is this image upscaler really free?
Yes. Upscaling runs in your browser on your own device, so there are no credits, no sign-up, no daily limit and no watermark.
Are my images uploaded?
No. The image never leaves your device. The page downloads the AI model once (about 5 MB) and processes the photo locally — you can check in your browser's network panel that no image is sent.
Which AI model does it use?
Real-ESRGAN general-x4v3, an open-source super-resolution model (BSD-3 license) that restores detail and removes blur and JPEG artifacts while enlarging 4×.
What do 2×, 4× and 8× mean?
2× and 4× are produced directly by the AI model. 8× is the AI's 4× result smoothly enlarged a further 2×, useful for printing small images.
What is the maximum size?
The result can be up to about 16 megapixels (for example 4096 × 4096). Pick a smaller scale for large photos; very large images can also exceed your browser's memory on phones.
Which formats are supported?
JPG, PNG and WebP in; PNG out, with the photo's orientation applied. Transparency is not preserved — transparent areas become white.
How long does it take?
Usually a few seconds to about a minute, depending on the image size and your device. Browsers with WebGPU are much faster.