4K Upscaler
A free 4K upscaler that sizes your photo to 3840 or 7680 px on the long edge, right on your device. No upload, no sign-up, no watermark.
or drop / paste an image here · JPG, PNG, WebP up to 20 MB
Runs in your browser. Your image is never uploaded.
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After4K vs 4x: What This 4K Image Upscaler Makes
4K is a target size. 4x is a multiplier. Here is what each one gives you from the same photo.
| 4K on this page | 8K on this page | A plain 4x upscale | |
|---|---|---|---|
| What it means | Long edge of 3840 px | Long edge of 7680 px | Each side times four |
| From a 382 x 512 photo | 2865 x 3840 px | 5730 x 7680 px | 1528 x 2048 px |
| From a 1920 x 1080 frame | 3840 x 2160 px (UHD) | 7680 x 4320 px | 7680 x 4320 px |
| Output size depends on | Only the aspect ratio | Only the aspect ratio | The size of your original |
| Model passes | One, or two if the source is under 960 px | One, or two if the source is under 1920 px | One |
| Measured on our test Mac, 382 x 512 photo | About 8 seconds | About 11 seconds | About 6 seconds |
| Fits on iPhone or iPad | Yes | Only if the pixel count fits the cap | Depends on the photo |
How to Upscale an Image to 4K
The 4K upscaler works in three steps inside your browser tab. The image never leaves your device.
- 1
Choose one image
Pick a JPG, PNG or WebP up to 20 MB. HEIC files from an iPhone are not supported yet, so export them as JPG first.
- 2
Pick 4K or 8K and press Upscale
The 4K upscaler enlarges your photo with an AI upscaling model until the long edge is exactly 3840 or 7680 px, keeping its proportions. Nothing is cropped or padded.
- 3
Compare and download
Drag the before/after slider to check faces, text and edges, then download the result. For a JPG, turn on Save as JPG and press Upscale again. Results are not saved once you close the tab.
Where a 4K Image Earns Its Pixels
A 4K image upscaler pays off where the picture fills a big screen or a big sheet of paper.
Desktop and TV wallpaper
A 16:9 picture comes out at 3840 x 2160, the native size of a UHD monitor or TV. Nothing is stretched by the screen afterwards.
Posters and wall prints
Divide pixels by the pixels per inch your printer asks for: a 3840 px edge prints 12.8 inches wide at 300 and 25.6 inches at 150. Use 8K for larger prints, and the DPI converter page if the file needs a DPI value.
Product photos with zoom
Zoomable shop galleries need a large file. Put a small supplier shot through the 4K upscaler, then check labels and logos against the original.
Slides and video projects
Drop a still into a 4K timeline or a large presentation so it fills the screen at its native size. With the 4K upscaler a 1080p frame becomes UHD in one model pass.
Digital photo frames and signage
A 4K display in a lobby or shop window shows every soft edge. Run older phone photos and web images through the 4K upscaler before they go on screen.
AI art and screenshots
When a generated image or a screenshot is too small for a wallpaper, the 4K upscaler brings it to screen size. For anime-style art, the waifu2x alternative page uses a model trained on drawings.
Before You Upscale a Picture to 4K
A few checks that make the 3840 px result look better and save you a second try.
- Start from the largest copy you have: from a 960 px long edge, the 4K upscaler reaches 3840 px in a single model pass.
- Crop first, then upscale, so every new pixel goes into the part you keep.
- Use the original file, not a screenshot of it or a copy sent through a chat app that compressed it.
- Convert HEIC photos to JPG before you open them in the 4K upscaler.
- Pick 8K only when you need it: it has four times the pixels of 4K and takes longer to make.
- Compare faces on the slider after upscaling, and open the downloaded file to see them at full size: skin can come out smoother than in the original.
- Check small text, logos and numbers: if they were blurry, the model may reshape letters.
- On an iPhone or iPad stick to 4K; an 8K result of a normal photo is over the roughly 16.7 million pixel limit there.