Password-protecting a ZIP file adds encryption so only someone with the password can extract the contents. But not all ZIP encryption is created equal — the method you use matters.
The built-in Windows ZIP tool does not support creating password-protected ZIP files. Windows can open them, but can't create them. You'll need a third-party tool.
7-Zip (Windows, free) is the best option. Right-click your files → 7-Zip → Add to archive. Set the archive format to ZIP, enter a password, and critically, change the encryption method from ZipCrypto to AES-256. ZipCrypto is the legacy default — it's fast but has known vulnerabilities and can be cracked with tools like pkcrack. AES-256 is the modern standard and is effectively unbreakable with a strong password.
On Mac, the built-in Archive Utility doesn't support password-protected ZIP creation either. Use Keka (free) — it creates AES-256 encrypted ZIP files through a simple drag-and-drop interface. Alternatively, from Terminal: `zip -e archive.zip files` creates a password-protected ZIP (but uses ZipCrypto, not AES-256).
For maximum security, use a strong password: 12+ characters, mix of letters/numbers/symbols, not based on dictionary words. And remember — the filename is not encrypted. Anyone can see what files are in the ZIP; they just can't extract them without the password. If filenames are sensitive, put the ZIP inside another encrypted ZIP, or use 7z format which supports filename encryption.