How to open Javadoc JAR file in web browser Rename the file entando-plugin-jpmail-5.3.2-javadoc.jar to entando-plugin-jpmail-5.3.2-javadoc.zip Use your favourite unzip tool (WinRAR / WinZIP) to extract it, now you have a folder entando-plugin-jpmail-5.3.2-javadoc Double click index.html will open the index page on your default web browser. How to generate Javadoc from a source JAR? Running the command javadoc: javadoc --ignore-source-errors -encoding UTF-8 -sourcepath "entando-plugin-jpmail-5.3.2-sources.jar" -d "entando-plugin-jpmail-5.3.2-javadoc" -subpackages