How to open Javadoc JAR file in web browser Rename the file wicket-http2-undertow-0.25-javadoc.jar to wicket-http2-undertow-0.25-javadoc.zip Use your favourite unzip tool (WinRAR / WinZIP) to extract it, now you have a folder wicket-http2-undertow-0.25-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 "wicket-http2-undertow-0.25-sources.jar" -d "wicket-http2-undertow-0.25-javadoc" -subpackages