Nightmare AI

Upscaling to 4K is the headline feature of Nightmare AI, and you can also pick HD or 2K if you want a smaller jump.

Nightmare AI is an online AI image upscaler that raises the resolution of a photo while cleaning up detail, so it also works as a photo enhancer and a way to unblur soft images.

It runs in the browser, so there is nothing to install.

Under the hood the service uses a Real-ESRGAN based model.

That family of models is known for sharpening low-resolution pictures rather than just stretching them.

Face correction is optional, which helps when you are working with portraits and want faces restored, and lets you leave it off for landscapes, product shots or anything without people in it.

The tool handles regular photos and anime-style artwork, so it covers both snapshots and illustrations.

If you have an old, small or blurry image that needs to hold up at a larger size, Nightmare AI is a direct way to try that.

Results will depend on how much detail the source image has to begin with.