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4K Image Upscaler

A 4K image upscaler that runs in your browser: enlarge a photo to 4K quality, with nothing uploaded.

4K Image Upscaler vs Upload Tools and a Plain Resize

Three ways to get a photo to 4K, side by side. The upload column describes online tools in general, not one product.

This toolUpload-based online upscalersPlain resize
Where the photo goesStays in your browserSent to a serverStays on your device
Sign-upNoneOften an account or creditsNone
Number of usesNo limitOften capped by creditsNo limit
DetailAI adds sharp detailAI adds sharp detailPixels are stretched, edges soften
4K targetOne button, 3840 px long sideOften a 2x or 4x choiceYou type the size
File typePNG or JPGVariesVaries

How to Use the 4K Image Upscaler

Three steps, and the photo never leaves your device.

  1. 1

    Add your photo

    Drop a JPG, PNG or WebP up to 20 MB onto the tool, or click to pick one. Use the original file, not a copy that was already enlarged or compressed again. The photo must be under 3840 px on its long side, or the tool tells you it is already 4K or bigger.

  2. 2

    Keep 4K selected

    The 4K button is the default and sets the long side to 3840 px, and your photo keeps its shape. Choose PNG to keep transparency or JPG for a plain photo, then press Upscale to 4K. A small photo can take two passes of the model to get there.

  3. 3

    Check and download

    The result appears next to your original. Zoom in on faces, text and fine edges, then download it. The file is named after your photo with a 4k suffix.

Is This 4K Image Upscaler Private? What to Expect

The photo stays on your device

The upscaling model runs in your browser, so the file is not uploaded for processing, and it never leaves your device. There is no sign-up, no credits and no limit on how many photos you upscale with this tool.

Limits you can hit

Files over 20 MB are not accepted, and a photo already at 3840 px or more is refused instead of being resized. Very large results can fail on older or low-memory devices. On an iPhone or iPad the output size is capped, and a 3840 px result fits under that cap.

It is AI output, so check it

The model invents detail it cannot see in the original, so the result is a good guess, not a recording of the real scene. Compare it with your original and look closely at faces, small text and repeating patterns before you use the file.

Frequently asked questions

In short, 4K quality means the photo has about four times the pixels of Full HD, enough to fill a 4K screen. On this page, 4K sets the long side of your photo to 3840 px.

It is sharp on large screens and in big prints, and it gives you room to crop. An upscaled photo gains pixels, but not the real detail a 4K camera would have captured.

Consumer TVs and monitors use 3840 x 2160. Digital cinema uses 4096 x 2160. This tool uses 3840 px on the long side and keeps your photo's shape.

The name rounds 3840 up to about four thousand pixels across. A 4K upscaler on this page uses that 3840 px width, so a 3:4 portrait comes out 2880 x 3840.

No. The photo is processed in your browser and never leaves your device. Site analytics are separate from the photo.

On an M-series Mac with WebGPU, 4K took about 2 seconds per photo, including the first model load. Without WebGPU the tool runs on the CPU and is much slower.

The 4K setting takes photos below 3840 px on the long side; a larger one is refused, because there is nothing left to enlarge. For a photo below 7680 px, choose 8K instead.

The tool only enlarges. If the long side is 3840 px or more, there is nothing to upscale, so it returns no file.

Yes, on iPhone and iPad the output is capped at about 16.7 megapixels. That is enough for 4K, but not for the 8K button.

Choose PNG to keep transparency, which is the default. Choose JPG when the photo has none. Each 4K PNG we saved was 13 to 14 MB.

It enlarges a photo and adds detail, but it is not built to deblur one. For a blurry shot, try the Unblur Image tool first.

Yes. It runs on your own device, so there is no sign-up, no credit card and no cap on photos.

It needs one to load the page and the model the first time. The photo itself is not sent anywhere.

The 8K button sets the long side to 7680 px, twice the width of 4K. It takes longer and the files are much bigger. Pick 4K for screens and most prints, and 8K only when you really need it. The 4K image upscaler button is the default for that reason.

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