A file with .mf extension is a Java Manifest file that contains information about the individual JAR file entries. The MF file itself is contained inside the JAR file and provides all the extension and package-related definition. JAR files can be produced to be used as an executable file. In such case, the mainfest file specifies the main class of the application that contains public static void main statement. Manifest files are named as MANIFEST.MF and can be opened with any text editor on Windows, MacOS and Linux Operating Systems.
Manifest File Format Specifications
Manifest file format specifications are available by Oracle in their guide for JAR file format. A Manifest file comprises of main sections that are followed by a list of sections for individual JAR file entries. Each section follows some rules and restrictions.
A main section:
contains information about security and configuration about the JAR file
contains information about the application or extension that the JAR file is part of
defines the main attributes for each individual manifest item
Note: No attribute in this section can be named “Name”.
An individual section defines various attributes for packages or files of a JAR file. Each section must start with an attribute named “Name” whose value must be a relative path to the file, or an absolute URL referencing data outside the archive.