OpenAnyFile
What is a .maff file?
Mozilla Archive Format is a data format developed by Christopher Ottley (MAF extension), first released in 2006. It is usually created by Old Firefox MAF add-on.
A ZIP of saved pages. The add-on no longer works in modern Firefox, but the archive opens here.
File details
| Full name | Mozilla Archive Format |
|---|---|
| Category | Data & science |
| MIME type | application/x-maff |
| Signature (magic bytes) | 50 4B 03 04 (ZIP) |
| Developer | Christopher Ottley (MAF extension) |
| Introduced | 2006 |
| Opens with | Archive browser |
| Uploaded? | No — read locally in your browser |
How to open a .maff file
OpenAnyFile routes .maff files to its archive browser, which shows a folder tree — open any file inside without extracting.
- Drop your .maff 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 archive browser.
- Use fullscreen for a closer look, check its checksums, or download it back unchanged.
What works — and what does not
Works
Viewing and inspecting: a folder tree — open any file inside without extracting. 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 .maff 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 .maff files
Can I open a .maff file without installing software?
Yes. OpenAnyFile opens .maff files in your browser using its archive browser. You get a folder tree — open any file inside without extracting, with nothing installed and no account.
How do I know a file is really a .maff file?
Check its first bytes instead of its name. A genuine MAFF file begins with 50 4B 03 04 (ZIP). OpenAnyFile shows the detected type, so a renamed file is easy to spot.
Is my .maff 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.