.j file: how to open it on Windows

2 Windows apps register the .j extension. Install one of them to open the file with a double-click.

• 
  XnView MP

  Professional Image Viewer & Photo Management

  Proprietary 1.12.2.0 436.9K ↓
• 
  SageThumbs

  A powerful shell extension allowing to preview enormous amount of image formats directly in Windows Explorer.

  Open source 2.0.0.23 14.6K ↓

Related guide: Change the default app for a file type in Windows