If you want to compress and reduce the size of a large EPUB file in Windows 11/10, ... you need to open OnlineConverter.com in a preferred web browser and make sure you are on its Compress EPUB page.

Yes, you can convert LIT to EPUB on Windows 11/10. LIT files are not as common as EPUB eBooks. So, you might want to convert them to EPUB to read them on other e-book devices.

The Windows 10 Creators Update gave Microsoft Edge the ability to open EPUB files stored on your PC. It immediately became easier to read your favorite books without having to download a separate app.