When a password makes sense
Some files shouldn't travel unprotected: tax returns, payslips, contracts, scans of IDs and passports, medical reports, bank statements, customer lists or HR documents. Email can be forwarded by mistake, attachments stay in inboxes for years and shared drives get reorganized. A password-protected ZIP adds a lock that travels with the files.
Common cases: an accountant sending a client's returns, an applicant sending ID documents to a landlord or an employer, a company sharing payroll files, or anyone backing up personal documents to a USB drive or cloud folder.
A password-protected ZIP is also a practical way to send many files at once. Some portals and email services accept a single attachment, and a ZIP turns a dozen documents into one file. Give the files clear names before zipping them, so the recipient knows what each one is after unlocking the archive, and check the total size against the email service's attachment limit.
AES-256 or ZipCrypto
AES-256 is the strong choice and the one to use for sensitive documents. Its only drawback is compatibility: Windows and macOS can't open AES-encrypted ZIPs on their own. The recipient needs a free program such as 7-Zip, WinRAR or The Unarchiver, or can open it in the browser with ConvertirDocs' Unzip tool, without installing anything.
ZipCrypto is the older method. Windows File Explorer opens it without extra software, which is convenient, but its encryption is weak and can be broken with readily available tools. Use it only when convenience matters more than real protection, never for highly sensitive files.
Good habits with the password
A ZIP is only as safe as its password. Use a long one, ideally a phrase of several words, and avoid birthdays or names. Never write the password in the same email as the attachment: send it by text message, phone call or a different chat. Agree in advance on how the recipient will open the file, especially if you choose AES-256.
Keep in mind that the password protects the content of the files. Depending on the program used to open it, the list of file names inside the ZIP may still be visible, so avoid putting sensitive information in the file names themselves.
Encrypted on your device
The ZIP is created and encrypted in your browser. Neither your files nor your password are uploaded to a server or stored. It is free, without an account and without limits beyond your device's memory. Whole folders can't be added in one step; select the files inside them. Photos and videos barely shrink, because they are already compressed.