How big is the result?

2K is about 2048 px on the long side; 4K is about 4096 px. The shape of your image is kept.

Does it invent detail?

An AI upscaler rebuilds detail the photo does not have, so it can guess tiny text or distant faces differently. The prompt asks it to keep everything as it is; compare with the slider before you use it.

Yes. Every AI image tool here is free to use, with or without an account, and there is no watermark. You get 10 images a day without signing in and 30 a day with a free SandBase account. The allowance resets at midnight UTC.

Are my photos stored?

No. Your photo is sent to the image model for this one request and the result comes straight back to your browser. Nothing is saved to a gallery. A copy of the result is kept in a short-lived cache for 24 hours so that pressing the button twice does not use two runs.

Does it work on my phone?

Yes. The tools work in any modern mobile browser. Tap the upload area to pick a photo or take one with the camera, then download the result to your photos.

Free · no sign-up

Free AI image upscaler to 4K

Make small, blurry or compressed images sharp: upscale to 2K or 4K with real detail in hair, skin, fabric and small text.

100% free
Up to 4K
Photos, art, text
No watermark

Sample result

Example

BeforeAfter

A 256 px parrot photo rebuilt at 2K with sharp feathers.

How to use the AI Image Upscaler

Three steps, on a computer or a phone.

1. Upload an imageA photo, a drawing or a screenshot, as JPG, PNG, WebP or HEIC.
2. Pick the type and sizePhoto, art or text, and 2K or 4K output.
3. Upscale and downloadCompare with the slider, then download the high-resolution JPG.

What people use it for

Old and small photosPhone photos from years ago, crops and thumbnails.
PrintingEnough pixels for posters, canvases and photo books.
Screenshots and artCrisp text and clean lines in slides, anime and logos.

More free AI image tools

All free, no sign-up, no watermark.

Need more control? Use the API

This tool runs on the SandBase image API. The API gives you every setting the free tool fixes for you.

Higher quality and sizeUp to 4K output and any aspect ratio, including extra-wide and tall.
Your own promptChange the template below, add reference images, or batch hundreds of images from your code or Agent.
No daily limitPay per image from one SandBase balance, with the same key for 2,000+ models and APIs.

API reference Image models and prices Get an API key

curl https://api.sandbase.ai/v1beta/models/google/gemini-nano-banana-2.1:generateContent \
  -H "Authorization: Bearer $SANDBASE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"contents":[{"role":"user","parts":[
        {"text":"Upscale and enhance this image to high resolution. Keep the content, composition, identity, faces, text, colors and ligh…"},
        {"inline_data":{"mime_type":"image/jpeg","data":"<base64 photo>"}}]}],
       "generationConfig":{"responseModalities":["IMAGE"],"imageConfig":{"imageSize":"4K"}}}'

The free tool uses this prompt template with your choices filled in.

Frequently asked questions

How big is the result?: 2K is about 2048 px on the long side; 4K is about 4096 px. The shape of your image is kept.
Does it invent detail?: An AI upscaler rebuilds detail the photo does not have, so it can guess tiny text or distant faces differently. The prompt asks it to keep everything as it is; compare with the slider before you use it.
Is it really free?: Yes. Every AI image tool here is free to use, with or without an account, and there is no watermark. You get 10 images a day without signing in and 30 a day with a free SandBase account. The allowance resets at midnight UTC.
Are my photos stored?: No. Your photo is sent to the image model for this one request and the result comes straight back to your browser. Nothing is saved to a gallery. A copy of the result is kept in a short-lived cache for 24 hours so that pressing the button twice does not use two runs.
Does it work on my phone?: Yes. The tools work in any modern mobile browser. Tap the upload area to pick a photo or take one with the camera, then download the result to your photos.