Are my images uploaded anywhere?

Signed out, the on-device upscaler never transmits your image. Complete an initial on-device upscale while online to cache the engine files, then try another image with Wi-Fi off before relying on offline use. Offline processing works while those files remain cached. You can also watch the browser's network inspector while it runs.

Two things send data, each one you choose: signing in uploads your finished upscales to your library and can include originals and previews, and a Cloud HD job uploads the file you picked for that job and processes it in the cloud. Cloud HD inputs are removed after the job; results stay in your library until you delete them.

The privacy policy linked in the footer lists exactly what an account stores and for how long.