Language selector and save as default

[blueisland]

I have a very simple dropdown box for two language selection (EN/FR) which I got from W3Schools. It works fine but what I want is that when the language is selected it becomes the default choice for visitors unless they choose otherwise. I assume this must involve a cookie but how do I code for this? I am using straight html, no CMS. Is it possible?

Thanks for any help

<div class="dropdown">
  <button class="dropbtn">EN</button>
  <div class="dropdown-content">
    <a href="https://websitename/fr/page.html">Français</a>
      </div></div>