OpenAnyFile
What is a .npz file?
NumPy Compressed Arrays is a data format developed by NumPy, first released in 2007. It is usually created by numpy.savez.
A ZIP of .npy files, one per array; each array's shape and values are listed here.
File details
| Full name | NumPy Compressed Arrays |
|---|---|
| Category | Data & science |
| MIME type | application/x-npz |
| Signature (magic bytes) | 50 4B 03 04 (ZIP) |
| Developer | NumPy |
| Introduced | 2007 |
| Opens with | NumPy reader |
| Uploaded? | No — read locally in your browser |
How to open a .npz file
OpenAnyFile routes .npz files to its NumPy reader, which shows the array shape, type and first values.
- Drop your .npz file on the box above, click it to choose the file, or paste it with Ctrl+V.
- The real format is detected from the file's first bytes — not just its name.
- The file opens in the NumPy reader.
- Use fullscreen for a closer look, check its checksums, or download it back unchanged.
What works — and what does not
Works
Viewing and inspecting: the array shape, type and first values. Size, type, signature and checksums are always shown.
Does not work
Editing and saving back. OpenAnyFile is a viewer, not an editor — for changes you still need the original app.
Is it safe to open a .npz file online?
Here, yes — because nothing is uploaded. Most "online viewers" send your file to their server. OpenAnyFile reads it with your browser's File API and decodes it on your own device, so there is no copy anywhere else. You can check: open your browser's network tab while opening a file — no upload appears.
Questions about .npz files
Can I open a .npz file without installing software?
Yes. OpenAnyFile opens .npz files in your browser using its NumPy reader. You get the array shape, type and first values, with nothing installed and no account.
How do I know a file is really a .npz file?
Check its first bytes instead of its name. A genuine NPZ file begins with 50 4B 03 04 (ZIP). OpenAnyFile shows the detected type, so a renamed file is easy to spot.
Is my .npz file uploaded anywhere?
No. The file is read locally by your browser and never sent to a server — it even works offline once the page has loaded.
Does it work on phones?
Yes — on Android and iPhone, in any modern browser. You can also install OpenAnyFile as an app.
Related formats
Other formats from the same family:
Format facts checked and page updated on September 25, 2026.