ZIP to GZ Converter
FileFlip converts ZIP to GZ entirely inside your browser, using libarchive compiled to WebAssembly. The file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. That means no file-size limit, no queue and no account.
How do I convert a ZIP file to GZ?#
- Drop your ZIP file onto the converter at the top of this page, or click it to pick one from your computer. You can add as many as you like.
- Leave the target set to GZ and the conversion starts on its own. FileFlip downloads 1.0 MB of WebAssembly the first time and nothing after that, then runs libarchive on your own machine.
- Save the GZ file. Your browser writes it straight to your downloads folder, because there was never a server holding it.
Does converting ZIP to GZ lose quality?#
No. Converting ZIP to GZ does not touch the files inside the archive. Each member is read out and written back byte for byte, so only the wrapper around them changes and nothing is recompressed.
Is it safe to convert ZIP files online?#
Yes, because nothing is uploaded. FileFlip converts ZIP files inside the browser tab you already have open, using WebAssembly builds of the same engines a desktop converter would install. Your file is read from your own disk into the page's memory, and no request carrying it is ever made.
You do not have to take that on trust. Open your browser's network panel, run a conversion, and you will see the engine come down and your file go nowhere. There is no upload, no server-side copy, no retention window, and no account tied to what you converted.
How FileFlip works lists every engine, its version and its download size, and shows how to check for yourself that nothing leaves your machine.
What ZIP to GZ actually does to the file#
Converting ZIP to GZ runs on libarchive, downloads 1.0 MB of WebAssembly the first time and nothing after that, copies the archived files through unchanged, keeps file contents.
| Engine | libarchive |
|---|---|
| Conversion path | 2 steps: ZIP → the unpacked files → GZ |
| Downloaded to your browser | 1.0 MB, once, then cached by your browser |
| Quality | Lossless, contents copied unchanged |
| You get back | One file |
| Where it runs | In a background worker, so the page stays responsive |
What survives the conversion
| What is in the file | This conversion | Why |
|---|---|---|
| File contents | Kept | Carried through into the converted file. |
| File timestamps | Sometimes | Survives for some files and not others. |
| File permissions | Sometimes | Survives for some files and not others. |
Worth knowing before you start:
- the output is a PAX tar archive inside the compressor, not a single compressed stream
- every entry is extracted into memory before anything is written, so a very large archive can exhaust it
- no passphrase is passed to the reader, so an encrypted archive cannot be opened
What is a ZIP file?#
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.
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.
What is a GZ file?#
A GZ file wraps a single DEFLATE-compressed stream in a header that can carry the original filename and modification time, plus a trailing CRC-32 checksum, as defined in RFC 1952.
Use GZ to compress a single file quickly, especially one going over HTTP, where gzip decoding is effectively free.
Convert GZ to XZ when the same data needs to be as small as possible and slower compression is an acceptable cost.
ZIP to GZ 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.