ZIP File Format (.zip)
A ZIP file is a container introduced by PKWARE in 1989 that holds any number of files and folders, each one compressed and stored as its own separate entry alongside a central directory listing them.
ZIP at a glance#
| Full name | ZIP archive |
|---|---|
| File extension | .zip |
| Category | Archives |
| Developer | PKWARE (Phil Katz) |
| First released | 1989 |
| MIME types | application/zipapplication/x-zip-compressed |
| Compression | Lossless |
| Specification | APPNOTE.TXT - .ZIP File Format Specification |
| FileFlip support | FileFlip reads and writes this format |
What a .zip file can hold#
These are the things a ZIP file either supports or does not, and they are what decides whether a conversion keeps everything or quietly drops something.
| Embedded metadata | Yes |
|---|---|
| Encryption | Yes |
Strengths and limitations of ZIP#
What ZIP does well
- Opens natively on Windows, macOS, iOS and Android without installing anything
- Extracting or replacing one file only touches that entry, not the whole archive
- Stable format that decades-old zip tools and today's tools both still read
Where ZIP falls short
- DEFLATE compression is clearly behind LZMA-based formats like 7z or xz on the same data
- The original ZipCrypto password scheme is cryptographically broken; only the newer, optional AES encryption is actually secure
- The original spec's 4 GiB file size and 65,535 entry limits still trip up tools that don't implement the ZIP64 extension
Use ZIP when the archive has to open on any device without the recipient installing anything, or when individual files need to be pulled out rather than the whole archive at once.
Convert away from ZIP when the same files need to be smaller for storage or transfer, since 7z or xz's solid compression usually beats it at the cost of that per-file random access.
How to open a .zip file#
A .zip file opens in the programs below, grouped by the platform you are on. If you would rather not install anything, FileFlip converts ZIP into a format your machine already opens, and it does it in the browser tab rather than on a server.
| Platform | Programs that open it |
|---|---|
| Windows | File Explorer, 7-Zip, WinRAR |
| macOS | Archive Utility, The Unarchiver, Keka |
| Linux | Archive Manager (File Roller), Ark, 7-Zip (p7zip) |
| iOS | Files |
| Android | Files by Google, ZArchiver |
| Web | FileFlip |
ZIP questions people ask#
Why can I open one file from a ZIP without extracting the whole thing?
A ZIP archive compresses each file inside it separately and lists them in a central directory at the end, so a tool can jump straight to one entry and decompress only that file. Formats like TAR.GZ compress everything as one continuous stream and don't have this shortcut.
Is a ZIP password actually secure?
It depends which encryption the ZIP uses. The original ZipCrypto method is weak enough to crack in seconds with widely available tools; only the newer AES-256 option, which not every zip program offers, is actually secure.
Why won't some old programs open a large ZIP file?
The original 1989 ZIP specification capped archives at 4 GiB and 65,535 files, and a tool that doesn't implement the ZIP64 extension added in 2001 fails on anything past that. Nearly every modern zip tool supports ZIP64, so this mostly comes up with older software.
What's the difference between ZIP and 7z?
ZIP compresses each file separately, which makes extracting a single item fast; 7z compresses the whole archive as one solid LZMA2 stream, which usually produces a smaller file but has to decompress more to reach an item near the end. 7z also isn't opened natively by Windows or macOS the way ZIP is.
Can a ZIP file contain other ZIP files?
Yes, a ZIP archive treats a nested .zip the same as any other file and stores it as an already-compressed entry, though compressing it again rarely shrinks it further since the inner archive's data is already dense.
Converting ZIP files#
Convert ZIP to another format
Convert another format to ZIP
Every conversion runs inside your browser. The file is read from your disk, the work happens on your own machine, and nothing is uploaded. How FileFlip works names the engine behind each family and how to verify that for yourself.