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How to open .WAR files on Windows

To open .WAR files on Windows, to run it: install and start a servlet container such as Apache Tomcat or Jetty, then deploy the .war (for Tomcat, place it in the host’s appBase/webapps directory, or use the Tomcat Manager application to deploy a WAR).

Step-by-step instructions

  1. To run it: install and start a servlet container such as Apache Tomcat or Jetty, then deploy the .war (for Tomcat, place it in the host’s appBase/webapps directory, or use the Tomcat Manager application to deploy a WAR).
  2. To inspect it: open the .war as an archive (it uses the Java archive/ZIP style) and look for folders like WEB-INF/classes and WEB-INF/lib.

Common issues

Copied the WAR but the app does not deploy or start

Servlet containers expect a specific web application structure inside the WAR. If required classes, libraries, or descriptors are missing or placed incorrectly, deployment can fail.

  1. Inspect the WAR contents and verify the standard layout exists (for example: WEB-INF/classes for your compiled classes and WEB-INF/lib for dependency JARs).
  2. If you use a deployment descriptor, confirm WEB-INF/web.xml is present and correctly packaged.
  3. Redeploy using your container’s documented method (for example, place the WAR in Tomcat’s appBase/webapps or deploy via the Tomcat Manager app).

Deployed application behaves differently than expected due to class/library loading

Servlet containers follow defined class loading and web application packaging rules. If you have duplicate libraries, incompatible versions, or misunderstand where classes should be placed, you can get runtime errors or unexpected behavior.

  1. Confirm libraries are packaged under WEB-INF/lib and your application classes under WEB-INF/classes (per common container deployment layouts).
  2. Remove duplicate or conflicting JARs in WEB-INF/lib and rebuild the WAR with a clean dependency set.
  3. Consult your container/spec documentation for how the container loads web application classes and resources.

Tried to open the WAR like a normal app and nothing runs

A WAR is a deployment package for a server-side web application; it is not an executable desktop application. It must be run by a servlet container.

  1. If your goal is to run the web app, deploy the WAR to a servlet container such as Tomcat or Jetty and access it through a web browser.
  2. If your goal is to inspect or extract contents, open it as an archive and review the files (WEB-INF, static assets, and libraries).

Security note

A WAR is server-deployed code: deploying an untrusted WAR to Tomcat/Jetty can execute attacker-controlled application logic within your server environment.

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