SAML protocol uses the base64 encoding algorithm when exchanging SAML messages. If you intercept a SAML Message, you will turn it in plain-text through base64 decoding.
Use this tool to base64 encode and decode a SAML Messages. Paste a plain-text SAML Message in the form field and obtain its base64 encoded version. Or, paste a base64 encoded SAML Message and decode it.