Key facts
- Each entry is stored with its own local header and compressed data, and a central directory at the end of the file lists every name, size, timestamp and CRC-32 checksum.
- MIME type is application/zip; files start with the bytes PK (0x50 0x4B), after Phil Katz, who created the format for PKZIP in 1989.
- Classic ZIP is limited to 4 GB per file and 65,535 entries; ZIP64 extensions remove those limits.
- Encryption is either legacy ZipCrypto (weak) or AES-256 as used by 7-Zip and WinZip.
- Formats such as .docx, .xlsx, .jar, .apk and .epub are ZIP archives with a fixed internal layout.
How to open a .zip file
Windows
Double-click to browse it in File Explorer or right-click and choose Extract All. Use 7-Zip for AES-encrypted, split or very large archives.
macOS
Double-click to extract it with the built-in Archive Utility. The Unarchiver or Keka handle encrypted archives and non-UTF-8 file names better.
Linux
Run unzip -l archive.zip to list the contents and unzip archive.zip -d output/ to extract (install the unzip package if needed).
Common problems and fixes
- "End-of-central-directory signature not found" or "The compressed folder is invalid"
- The download was cut short, or the file is one part of a split archive. Re-download it, or put all .z01/.z02 parts in one folder and open the .zip with 7-Zip.
- CRC error or some files fail to extract
- Part of the data is damaged, so those entries no longer match their stored checksums. Extract the intact entries with 7-Zip or a recovery tool and get a fresh copy for the rest.
- Windows cannot extract a password-protected ZIP
- File Explorer only supports legacy ZipCrypto, not AES-256. Open the archive in 7-Zip and enter the password there.
- File names look garbled after extraction
- The archive was created with a legacy code page instead of UTF-8. Extract it with 7-Zip or The Unarchiver, or on Linux use unzip -O CP936 (or the matching encoding).
- "Path too long" errors on Windows
- Extract to a short folder such as C:\x, or enable long path support and extract with 7-Zip.
Often converted to or from: TAR.GZ, TAR, 7Z, RAR, ISO