Extension: sys

What is it? Windows System file (most common)

Where’s it from? A sys file stores system settings and variables used by the Windows and MS-DOS operating systems. The information is stored in plain text and is often understandable by humans, i. e., PATH=C:\WINDOWS\SYSTEM32.

How do I use it? While it is possible to alter sys files using any text editor or word processor, only advanced users who really know what they’re doing should attempt it. The wrong edit can cause your computer not to start, or to crash unexpectedly.

Can I safely delete or move it? No.

Can it be dangerous? No.

–David Hakala