Why Windows hides this by default
Windows hides file name extensions out of the box mainly to keep the interface looking simpler for everyday use, on the assumption that most people care about a file's icon and name, not its extension. In practice, this default trades a small amount of visual simplicity for a real blind spot: a file that appears to be named 'invoice.pdf' could actually be 'invoice.pdf.exe,' with the truly dangerous part of the name hidden from view.
What to check for once extensions are visible
With extensions turned on, it's worth getting into the habit of glancing at the actual extension before opening anything unexpected, especially email attachments or downloads from unfamiliar sources. A document that should be a .docx or .pdf but is actually an .exe, .scr, or .bat file is a strong warning sign, since ordinary documents are never legitimately packaged as executable files.
Frequently Asked Questions
Does turning this on change how my files are organized?
No -- this setting only affects what's displayed in File Explorer. It doesn't rename, move, or modify any files themselves.
Will this setting stay on after I restart my computer?
Yes, it's a persistent File Explorer setting that stays enabled across restarts until you manually turn it back off.