What is the ZIP file format?
.zip is currently the most popular format used for archiving and compressing files and folders. Creating archives using the ZIP compression method is lossless, and enables reducing the size of chosen files and folders.
The .zip format supports compression through several algorithms. Depending on the version, these include (among others):
- Deflate (most common)
- BZIP2
- LZMA / LZMA2
- Implode (legacy)
- WavPack
- Zstandard (added in newer APPNOTE revisions)
Advantages of ZIP compression
All files compressed with the ZIP method are stored separately within the archive, which makes it possible to extract individual entries without decompressing the whole set. Files within an archive are not only stored separately but also compressed individually, which enables substantially reducing the final size of a given file. The format also supports optional AES-256 encryption for securing individual entries.
The .zip design is also notable in that many modern file formats are themselves .zip containers - including .DOCX, .XLSX, .EPUB, and Android .APK packages. The signature bytes at the start of every standard .zip file - 50 4B 03 04 - encode the initials of ZIP's creator, Phil Katz ("PK").
ZIP archiving and compression is used by many people and programs for the purpose of merging extensive file structures into a single file, which facilitates sending and transferring files.
Differences between ZIP, RAR and 7Z
The .zip format was developed in 1989, before other currently popular archive formats. It typically uses the light and fast Deflate compression algorithm. In competing formats such as .RAR and .7Z, a series of improvements - including better compression ratios and stronger encryption - were introduced, though at the cost of higher memory requirements and slower processing compared with .zip. ZIP's enduring strength is near-universal compatibility: virtually every operating system and countless applications can open a .zip file natively, without additional software.
Security & safety
RISK: MEDIUMZIP itself is safe, but it is a top malware-delivery wrapper: attackers email ZIPs to bypass scanners and hide an EXE or script inside (sometimes inside a password- protected ZIP whose password is in the email body, defeating antivirus). Treat unexpected ZIP attachments with suspicion and check the contents before running anything executable. "Zip bombs" (tiny archives that expand to terabytes) can crash naive extractors. On the privacy side, standard ZipCrypto passwords are weak and crackable in seconds - for real protection use AES-256 (7-Zip, WinZip, PeaZip).
Format details
in a nutshellPrograms that open ZIP files
Windows5 apps
WinZip
Paid Open the ZIP and click 'Unzip'. The original commercial tool - rarely needed now that Windows unzips natively. 
7-Zip
Open-source Right-click > 7-Zip > 'Extract Here' / 'Extract to folder'. Best free tool; also creates AES-256 encrypted ZIPs. 
PeaZip
Open-source Open the ZIP and click Extract. Free, supports AES-256 and split archives. (Note: old peazip.org URL moved to peazip.github.io.) 
Windows File Explorer (built-in)
Built-in Right-click the ZIP > 'Extract All…', choose a folder, click Extract. Or double-click to browse inside without extracting. 
macOS3 apps
The Unarchiver
Free Free App Store app for ZIPs Archive Utility struggles with (encoding, split, password). Right-click > Open With.
Archive Utility (built-in)
Built-in Double-click the ZIP - macOS extracts it automatically into the same folder. 
Linux4 apps
Xarchiver
Open-source Lightweight GUI archiver for XFCE/LXDE: open and Extract. (Active fork on GitHub; old SourceForge page is stale.)
File Roller (GNOME Archive Manager)
Open-source Double-click the ZIP in Files, then 'Extract'. Bundled with GNOME. (Project now lives on GNOME GitLab, not the old SourceForge URL.)
unzip (command line)
Open-source Run: unzip archive.zip - the standard Info-ZIP tool on most distros. 
Android1 app
Files app (built-in)
Built-in Tap the ZIP in the Files app - iOS unzips it into the same folder (since iOS 11, 2017). Technical details
deep spec| MIME type | application/zip |
| Magic bytes | 50 4B 03 04 ("PK\x03\x04") at offset 0 - "PK" are Phil Katz's initials |
| File structure | Central directory stored at the END of the archive, enabling appending files and self-extracting EXE stubs before the first entry |
| Compression per entry | Each file is compressed independently, allowing selective extraction without decompressing the whole archive |
| Default compression | Deflate (method 8); uncompressed storage also available (method 0 - Store) |
| Supported algorithms | Deflate, BZIP2, LZMA, LZMA2, WavPack, Zstandard (support varies by implementation) |
| Encryption | Optional per-entry AES-256 (since PKZIP 5.0) and legacy ZipCrypto (weak - avoid for sensitive data) |
| Large file support | ZIP64 extension removes the classic 4 GB per-entry and 65,535-entry limits |
| Split archives | Multi-volume spanning via numbered segments (.z01, .z02, …) |
| Integrity check | CRC-32 checksum per entry, stored in both local header and central directory |
| Unicode filenames | UTF-8 encoding flag (general-purpose bit 11) standardized in APPNOTE 6.3.0 |
| Self-extracting archives | EXE stubs can be prepended; the embedded central directory keeps the file valid as both EXE and ZIP |
| Archive comments | Archive-level and per-entry comments stored as plain text in the central directory |
| Used as base format | DOCX, XLSX, EPUB, APK, JAR, and ODF files are all ZIP containers with structured internal content |
| Native OS support | Built into Windows Explorer (since XP), macOS Finder, and standard Linux distros via unzip/zip |
| Released | 1989 (PKZIP 1.0); APPNOTE specification is public |
| Open standard | Yes · royalty-free |
| Specification | pkware.cachefly.net |
ZIP conversions
Community Q&A
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