While not a common everyday format like .docx or .jpg , the .vac extension is frequently associated with:
If the file is located in a /temp/ or /cache/ directory and the timestamp (May 2021) is years in the past, it is almost certainly a stale artifact. However, if this file is in a production environment associated with security software (like Kaspersky), moving it to a "quarantine" folder for 48 hours before deletion is the safest path. Final Thoughts 1621058650.vac
If you've found this file on your server or within a project folder, you’re likely asking two questions: What is it? and Can I delete it? 1. Decoding the Filename The structure of 1621058650.vac gives us two major clues: While not a common everyday format like