What is a .zip file?

About the format

A .zip file is the universal compressed archive: multiple files and folders packed into one, with lossless compression, supported natively by every modern operating system — Windows opens it in Explorer, no extra software needed. Its ubiquity gives it two lives. The mundane one: email attachments, downloads, backups, and the container format hiding inside many others (.docx, .xlsx, .jar and Android .apk files are all ZIPs with rules). The security-relevant one: malware routinely ships inside archives, sometimes password-protected specifically so email scanners can't inspect the contents — a password-protected ZIP from an unexpected sender, with the password helpfully in the email body, is a pattern worth treating as hostile on sight. The archive itself doesn't execute; the risk is always what you run after extracting. Extract first (right-click → Extract All), then judge the contents by their real extensions — an 'invoice.pdf.exe' inside a ZIP is the payload, the ZIP was just the envelope.

How to open a .zip file

Is a .zip file dangerous?

The archive is a container. The judgement call is about what's inside — especially executables, scripts and shortcuts.

Related file types