About the MAFF file format
MAFF files are standard ZIP files containing one or more web pages, images, or other downloadable content. Additional information, like the original page address, is saved along with the content; this metadata allows the browser to open these files intelligently.
MAFF, compared to other web archive formats, is particularly suited to package video and audio together with related web resources. This ability derives from the basic structure of the ZIP container, where compression can be used for web pages, and verbatim storage for content that require fast streaming access and wouldn't benefit from being re-compressed, like most video and audio formats.
Features of the MAFF file format
Store web content in a single file
The various files required to view a saved page as it appeared on-line are saved together, and cannot be separated by accident.
Store multiple independent pages in the same archive
For example, Firefox with the MAF extension is able to save all the open tabs in a single file.
Based on the ordinary ZIP / JAR format
The ZIP format is supported natively on many modern operating systems. The contents of MAFF archives can be extracted using any ZIP extractor. The single files that are saved along with the main web page can be easily separated and inspected, in their original form, while preserving the advantages of storing the related content in a single file.
Web pages in MAFF files are compressed, not encoded, with the result of the archive being often much smaller than the original web content.
Suited for video and audio files
Since compression is used for web pages but not for already compressed content, most multimedia formats stored in MAFF files can be opened without the requirement of uncompressing the entire file. For example, this enables seeking instantly to the middle of a video, either stored locally or remotely available through a streaming source.
View using the jar: protocol
Even without the MAF extension, Mozilla browsers are able to display the contents of MAFF archives natively, using the jar: protocol.
Store metadata about the saved resources
MAFF archives contain metadata like the original URL the page was saved from and the date/time of the save operation. The presence of this additional data is indifferent to ordinary ZIP extractors, but for example allows the Firefox browser with the MAF extension to perform operations like:
- Opening the original page instead of the archived copy while on-line
- Enabling off-line navigation between pages in different archives
- Refreshing the archive contents with the latest on-line version (not implemented in MAF at present)
- Asking web services like the Internet Archive about how the page appeared at the time it was saved (not implemented in MAF at present)
Store arbitrary extended metadata
Extended metadata may include the browser's scroll position in the page, text zoom level, and more. The MAF extension for Mozilla browsers has an option to store this kind of data, even though the current version is not able to read it.
Supported by Open Source products
The MAF add-on enables Mozilla-based browsers to handle MAFF archives intelligently. The latest version is distributed under a choice of several Open Source and Free Software licenses: the Mozilla Public License 1.1, the GNU General Public License 2.0, the GNU Lesser General Public License 2.1, or any later version of these licenses. This means that the add-on will always remain available under one of these licenses in the future.
There is no risk of vendor lock-in not only because of the open file format, but also because the MAF extension allows batch conversion of already saved MAFF files to other web archive formats at any time.
More information about the MAFF file format can be found in the MAFF specification.