whats the extension of a markup language code example

Example 1: whats the extension of a markup language

svg style="display:none;">
  <symbol id="down" viewBox="0 0 16 16">
    <polygon points="3.81 4.38 8 8.57 12.19 4.38 13.71 5.91 8 11.62 2.29 5.91 3.81 4.38" />
  </symbol>
  <symbol id="users" viewBox="0 0 16 16">
    <path d="M8,0a8,8,0,1,0,8,8A8,8,0,0,0,8,0ZM8,15a7,7,0,0,1-5.19-2.32,2.71,2.71,0,0,1,1.7-1,13.11,13.11,0,0,0,1.29-.28,2.32,2.32,0,0,0,.94-.34,1.17,1.17,0,0,0-.27-.7h0A3.61,3.61,0,0,1,5.15,7.49,3.18,3.18,0,0,1,8,4.07a3.18,3.18,0,0,1,2.86,3.42,3.6,3.6,0,0,1-1.32,2.88h0a1.13,1.13,0,0,0-.27.69,2.68,2.68,0,0,0,.93.31,10.81,10.81,0,0,0,1.28.23,2.63,2.63,0,0,1,1.78,1A7,7,0,0,1,8,15Z" /> 
  </symbol>
   
  <!-- more symbols here -->
</svg>

Example 2: whats the extension of a markup language

svg style="display:none;">
  <symbol id="down" viewBox="0 0 16 16">
    <polygon points="3.81 4.38 8 8.57 12.19 4.38 13.71 5.91 8 11.62 2.29 5.91 3.81 4.38" />
  </symbol>
  <symbol id="users" viewBox="0 0 16 16">
    <path d="M8,0a8,8,0,1,0,8,8A8,8,0,0,0,8,0ZM8,15a7,7,0,0,1-5.19-2.32,2.71,2.71,0,0,1,1.7-1,13.11,13.11,0,0,0,1.29-.28,2.32,2.32,0,0,0,.94-.34,1.17,1.17,0,0,0-.27-.7h0A3.61,3.61,0,0,1,5.15,7.49,3.18,3.18,0,0,1,8,4.07a3.18,3.18,0,0,1,2.86,3.42,3.6,3.6,0,0,1-1.32,2.88h0a1.13,1.13,0,0,0-.27.69,2.68,2.68,0,0,0,.93.31,10.81,10.81,0,0,0,1.28.23,2.63,2.63,0,0,1,1.78,1A7,7,0,0,1,8,15Z" /> 
  </symbol>
   
  <!-- more symbols here -->
</svg>