Apache Tomcat is a common and frequently used open-source Java servlet container that implements Oracle’s Java Servlet and JavaServer Pages (JSP) specifications. By doing so, Tomcat provides the means to run Java code in a web server environment. Java programmers love it because they can write web applications in a language they already know. Tomcat can be used as a standalone pure-Java web server, but is often used in conjunction with the regular Apache or another general purpose web server. In those instances, Tomcat serves requests from the other web server.