How to open Javadoc JAR file in web browser Rename the file r2-netty-27.7.18-javadoc.jar to r2-netty-27.7.18-javadoc.zip Use your favourite unzip tool (WinRAR / WinZIP) to extract it, now you have a folder r2-netty-27.7.18-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 "r2-netty-27.7.18-sources.jar" -d "r2-netty-27.7.18-javadoc" -subpackages