32 formats: 21 written here, from ZIP (levels 0 to 9, AES-256 or ZipCrypto password) and 7Z to every common tarball, single-file GZ, BZ2 and XZ, and the Java archives. RAR, CAB, DEB, RPM, XAR and LHA are unpacked so their files can be packed again. Everything is packed on your device, then opened again to check every file came back identical. Nothing is uploaded.
The level is the main choice an archive tool gives you. This packs the files above (or the sample project) as ZIP at all ten levels, then as TAR.GZ, TAR.BZ2, TAR.XZ and 7Z, timing each run on this device.
This page writes WinZip AES-256 (AE-1): a key stretched from your password with 1,000 rounds of PBKDF2-SHA1, AES in counter mode, and a 10-byte HMAC that catches tampering. Here is the first entry of the archive you just made, byte by byte.
Click a format this page writes to pick it above. Levels apply where the format has a level; TAR, ISO, CPIO and AR only bundle, so they come out about the size of the files plus headers.