Is a .DAT File a Virus or Safe to Delete?
Short answer: a .dat file is almost always plain data belonging to some program, not malware. Whether it is safe to delete depends entirely on where it lives and which app created it.
The verdict
Rarely a virus; safe to delete only if it is orphaned. .dat is a catch-all extension meaning "data" — it has no single format. A program simply dumps whatever it wants into a .dat file. That makes the extension itself meaningless for judging safety: what matters is the program that owns it and where the file sits.
The three common cases
- App data inside a program's folder. If the
.datis inside an application's install or settings folder, it holds that program's data (a database, cache, or config). Leave it — deleting it can corrupt the app's state. Not a virus. - winmail.dat in an email. This is Outlook's proprietary TNEF attachment wrapper. It is not malware; it just holds the real attachment in a format only Outlook writes cleanly. Open it with a TNEF viewer (or ask the sender to resend in a normal format). Safe to discard once you have the contents.
- A stray .dat you cannot trace. A random
.datin Downloads or a temp folder is usually leftover data and is safe to delete. Only worry if it is an executable in disguise.
Could a .dat be a virus?
The data inside a .dat cannot run by itself — it is inert. Malware sometimes ships a real executable hidden with a .dat name to look harmless, but it would need another program to launch it. If a .dat appeared after you ran an unknown installer, scan it with Windows Security or an on-demand scanner before deleting.
How to check what made it
Open the file in a plain text editor and read the first few lines: readable text or a recognisable header often reveals the source program. If it is unreadable binary and lives inside an app folder, leave it alone.
FAQ
Is a .dat file a virus?
Not by itself — a .dat holds inert data and cannot execute. Malware occasionally uses a .dat name to disguise a payload, but it needs another program to launch it. Scan any .dat that appeared from an unknown source.
Is it safe to delete a .dat file?
Only if it is orphaned (in Downloads or a temp folder). A .dat inside an application's folder is that program's data — deleting it can corrupt the app. winmail.dat is safe to delete once you have extracted the attachment.
What is winmail.dat and is it dangerous?
It is Outlook's TNEF attachment wrapper, not malware. It holds the real attachment in a format only Outlook writes. Open it with a TNEF viewer, then it is safe to discard.