Direct answer
ZipCrypto usually has the widest legacy ZIP support. AES-encrypted ZIP files require compatible extraction software. The 7z and RAR5 formats provide strong options but are not universally handled by built-in operating-system extractors.
Compatibility matrix
Goal
Practical choice
Old or unknown extractor
Do not send sensitive data merely to preserve ZipCrypto compatibility; choose a secure sharing channel instead.
Known 7-Zip users
7z with AES-256 and encrypted file names is a practical strong option.
Known WinRAR users
RAR5 with a strong password and encrypted file names can be appropriate.
Standards-based ZIP workflow
Use AES-enabled ZIP and test the exact recipient tools.
Run a harmless interoperability test
- Create a small test file with no sensitive content.
- Archive it using the intended format and encryption method.
- Transfer it through the real delivery channel.
- Open it on each required platform with the recipient’s approved tool.
- Confirm file names and contents behave as expected.
