What is the Z02 file format?
Files with the .z02 extension are part of a split ZIP archive - specifically the second volume in a multi-part set. The naming convention is defined by PKWARE's APPNOTE specification and is supported by WinZip, 7-Zip, WinRAR, and most other modern archivers.
.z02 is a binary format. Inside, it carries a raw continuation of the host ZIP byte stream - compressed data produced by the DEFLATE algorithm (or STORE for data that is already compressed). The compression replaces repetitive byte patterns with shorter symbol sequences, which can reduce the original data size by up to 60 percent depending on content type. Unlike a standalone archive, a .z02 file holds no index and no central directory - those live exclusively in the final .zip part of the set.
.z02 files are generated automatically when an archive is divided into smaller parts of a chosen size. Splitting is useful when you need to send large data via email, upload to a cloud storage service, or write to fixed-capacity media, all of which impose file-size limits. The first volume is saved as a .z01 file, the second as .z02, the third as .z03, and so on; the last segment keeps the .zip extension because it contains the central directory.
To unpack the archive, all parts must be present in the same folder. You open the final .zip file and your archive tool reassembles the volumes automatically. Attempting to open a .z02 file in isolation will fail - the file is meaningless without the other segments.
Security & safety
RISK: MEDIUMA split ZIP carries the same risks as any ZIP - it can contain malware, visible only after extraction, so scan unexpected archives before running anything inside. The .z02-specific issue is completeness, not security: if any part is missing (the final .zip that holds the index, or a middle volume like .z02 that the data streams through), the archive won't extract and the missing bytes cannot be recovered. Verify you have a continuous set (.z01, .z02 … plus the .zip) before relying on it. Beware fake 'z02 opener' sites bundling adware - any mainstream archiver opens these.
Format details
in a nutshellPrograms that open Z02 files
Windows4 apps
WinZip
Paid Open the final .zip part (not the .z02) with all segments in the folder. WinZip created this split-volume scheme. 
WinRAR
Paid Gather all parts in one folder, then open/extract the last .zip; WinRAR joins the .z01/.z02… volumes automatically. 
7-Zip
Open-source Put all parts in one folder. Right-click the FINAL .zip > 7-Zip > Extract Here. (Opening the .z02 directly won't work.) Free. 
PowerArchiver
Paid Open the final .zip with every volume present in the same folder; PowerArchiver reassembles the split set. 
macOS2 apps
The Unarchiver
Free Place all parts together and open the final .zip; The Unarchiver handles split ZIP volumes. macOS Archive Utility usually cannot. 
Linux2 apps
Xarchiver
Open-source Open the final .zip with all volumes present in the same directory. (Active fork on GitHub.) 
7-Zip / p7zip
Open-source Gather the parts and run: 7z x archive.zip (the final part). It reads the .z01/.z02 siblings automatically. Technical details
deep spec| Format type | Second volume of a multi-part (split) ZIP archive; binary format |
| Encoding | Binary |
| Byte order | Little-endian |
| Compression algorithm | DEFLATE (per-entry, inherited from host ZIP); STORE used for already-compressed data |
| Volume size | Fixed to the chosen split size (e.g. 25 MB, 100 MB, 700 MB, 4 GB); all middle volumes are the same size |
| File signature (magic bytes) | None - no fixed header; begins mid-stream as a raw continuation of the ZIP byte stream; not self-identifying |
| Central directory | Absent from .z02; the ZIP central directory and end-of-central-directory record reside only in the final .zip volume |
| Integrity verification | Per-entry CRC-32 checksums; verifiable only after all volumes are assembled, as the index lives in the final .zip |
| Encryption | ZipCrypto or AES-256 (WinZip AE-1/AE-2) inherited from the host archive; applied archive-wide, not per volume |
| ZIP64 support | Yes, when the host archive uses ZIP version 4.5+; removes the 4 GB per-file limit and extends entry count to 2^64 |
| MIME type | application/zip (primary); application/octet-stream also used |
| Naming convention | .z01 (first volume), .z02 (second), .z03 (third), …; the final segment always carries the .zip extension |
| Maximum file entries | 65,535 in standard ZIP; up to 2^64 with ZIP64 - the entry table is stored only in the final .zip |
| Operating systems | Windows, macOS, Linux, and any platform with a split-ZIP-capable archiver |
| Released | Split/spanned ZIP defined in PKWARE APPNOTE; .z01/.z02 naming used by WinZip and compatible tools |
| Latest version | Follows the host ZIP APPNOTE (6.3.x); the volume itself carries no separate version |
| Open standard | Yes · royalty-free |
| Specification | pkware.cachefly.net |
Z02 conversions
Community Q&A
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