What is the MAFF file format?
A .maff file is a web-page archive stored inside a standard ZIP archive. The Mozilla Archive Format extension for Firefox - developed by Paolo Amadini - saved complete web pages, including all embedded images, stylesheets, and scripts, into a single .maff container.
Inside the archive, each saved page occupies its own numbered subdirectory. That subdirectory holds the main .html file, all referenced resources, and a ^metadata^ subfolder containing an RDF/XML file that records the original URL and the save timestamp.
Because .maff is a valid ZIP file, you can rename it to .zip and inspect its contents in any archive manager such as 7-Zip. Compression uses DEFLATE, giving .maff a size advantage over the base64-encoded MHTML format, which inflates file size by roughly one-third. Unlike MHTML, a single .maff archive can hold multiple saved pages - each in its own top-level subdirectory.
The Firefox extension that created .maff files supported Firefox up to version 56 (2017). When Firefox switched to the WebExtensions API in version 57, the extension was not updated and was discontinued in 2018. No other mainstream browser ever supported .maff natively. Users migrating away from .maff typically switch to WebScrapBook or SingleFile, which save pages in different formats.
Security & safety
RISK: LOWMAFF files are ZIP archives containing saved web pages (HTML + assets). No different from opening any saved HTML page. Risk is the same as opening any archived web content: embedded JavaScript from the original page may attempt network requests or contain malicious scripts. Open in a browser with script execution if you trust the source; inspect the HTML files in a text editor first if uncertain.
Format details
in a nutshellPrograms that open MAFF files
Windows3 apps
7-Zip (manual extraction)
Open-source Rename .maff to .zip, then right-click → Open archive with 7-Zip. Navigate to the page subdirectory and open the HTML file in a browser.
WebScrapBook (Firefox extension)
Open-source Install WebScrapBook in Firefox 57+ or Chrome. It can open and browse MAFF archives via its viewer. File → Open Archive → select .maff.
OpenMAFF
Open-source A standalone Windows utility to open and browse MAFF files without Firefox; extracts content and opens the page in the default browser. 
macOS1 app
The Unarchiver / Archive Utility (manual extraction)
Free Rename .maff to .zip, then double-click to extract with Archive Utility or The Unarchiver. Open the HTML file inside in Safari/Chrome/Firefox. 
Linux2 apps
7-Zip / unzip (manual extraction)
Open-source unzip file.maff -d output/ - then open the HTML file in a browser. Or use file-roller / Ark GUI archive manager.
WebScrapBook (Firefox extension)
Open-source Install WebScrapBook extension in Firefox; use its archive viewer to open the .maff file. Technical details
deep spec| Container format | ZIP archive (magic bytes `50 4B 03 04` at offset 0) |
| Compression | DEFLATE per entry (standard ZIP compression) |
| MIME type | application/x-maff (also application/zip) |
| Internal page layout | One numbered first-level subdirectory per saved page |
| Metadata storage | `^metadata^` subfolder per page; RDF/XML file with original URL and save timestamp |
| Multi-page support | Yes - multiple web pages in one archive, each in its own top-level subdirectory |
| Resource bundling | HTML, images, CSS, and JS stored together in the page subdirectory |
| Integrity | ZIP CRC-32 per entry |
| Byte order | Little-endian (ZIP standard) |
| Typical file size | 50 KB - 50 MB (depends on page complexity and embedded media) |
| Creator tool | Mozilla Archive Format Firefox extension by Paolo Amadini; discontinued 2018 |
| Firefox support window | Firefox 2-56 (2007-2017); incompatible with WebExtensions API (Firefox 57+) |
| Manual inspection | Rename `.maff` to `.zip` to open in any archive manager |
| Maximum ZIP entries | 65,535 (standard ZIP limit); ZIP64 supports larger archives |
| Released | 2004 (Mozilla Archive Format Firefox extension) |
| Latest version | Final extension release supports Firefox up to version 56 (ESR, 2017); extension discontinued 2018 |
| Specification | www.amadzone.org |
MAFF conversions
Community Q&A
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