By default Tomcat supports following auth-method's with corresponding Authenticators. 1. BASIC - org.apache.catalina.authenticator.BasicAuthenticator 2. FORM - org.apache.catalina.authenticator.FormAuthenticator 3. DIGEST - org.apache.catalina.authenticator.DigestAuthenticator 4. CLIENT-CERT - org.apache.catalina.authenticator.SSLAuthenticator My previous post explains how BASIC authentication wor