Plain HTML
<html>
  <body
      onload="document.forms[0].submit()">
    <form
        method="POST"
        action="https://aai-demo-idp.switch.ch/idp/profile/SAML2/POST/SSO">
      <input
          type="hidden"
          name="RelayState"
          value="ss:mem:23e3a3b1268acd89dc226bb1ce0d0c6ba7ecf773"/>
      <input
          type="hidden"
          name="SAMLRequest"
          value="
            PHNhbWxwOkF1dGhuUmVxdWVzdCB4bWxuczpzYW1scD0idXJuOm9hc2lzOm5h
            ...
            YXRlPSIxIi8+PC9zYW1scDpBdXRoblJlcXVlc3Q+"/>
    </form>
  </body>
</html>
SAML request (Base64 decoded)
<samlp:authnrequest xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"
    assertionconsumerserviceindex="1"
    destination="https://aai-demo-idp.switch.ch/idp/profile/SAML2/POST/SSO"
    id="_f2f27516ec08af29501c749629b119d3"
    issueinstant="2008-02-27T12:17:40Z"
    version="2.0">
  <saml:issuer xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">
    https://aai-demo.switch.ch/shibboleth
  </saml:issuer>
  <samlp:nameidpolicy xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"
      allowcreate="1"/>
</samlp:authnrequest>