File Extension Lookup
Look up common Windows file extensions. The letters at the end of a name tell you the usual file type, they do not prove a file is safe.
How this tool works
Search matches names like pdf, .PDF, and "PDF file" against a local list of common types. Results explain what the type is for, what usually opens it, and when deleting it is a bad idea.
Important limitations
Thousands of extensions exist. Unknown types are omitted on purpose rather than guessed. When in doubt, do not run a file from an email.
Frequently asked questions
Windows doesn't show extensions.
In File Explorer: View → Show → File name extensions. That makes fake "PDF" programs easier to spot.