The 600MB version is a "Ship of Theseus" paradox—by removing 85% of the OS to achieve that size, it is no longer a reliable, secure, or truly functional version of Windows 8.1. You lose critical security updates, core drivers, and system stability. In the long run, the time saved on the download is lost tenfold in troubleshooting "missing DLL" errors and cleaning malware.
(much safer, 300–800 MB):
: Since 8.1 is no longer supported, it is highly recommended to upgrade to Windows 10 or 11 for continued security updates. Windows 8.1 Highly Compressed 600mb