[forms] Can you require two form fields to match with HTML5?

As has been mentioned in other answers, there is no pure HTML5 way to do this.

If you are already using JQuery, then this should do what you need:

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$(document).ready(function() {_x000D_
  $('#ourForm').submit(function(e){_x000D_
      var form = this;_x000D_
      e.preventDefault();_x000D_
      // Check Passwords are the same_x000D_
      if( $('#pass1').val()==$('#pass2').val() ) {_x000D_
          // Submit Form_x000D_
          alert('Passwords Match, submitting form');_x000D_
          form.submit();_x000D_
      } else {_x000D_
          // Complain bitterly_x000D_
          alert('Password Mismatch');_x000D_
          return false;_x000D_
      }_x000D_
  });_x000D_
});
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<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>_x000D_
<form id="ourForm">_x000D_
    <input type="password" name="password" id="pass1" placeholder="Password" required>_x000D_
    <input type="password" name="password" id="pass2" placeholder="Repeat Password" required>_x000D_
    <input type="submit" value="Go">_x000D_
</form>
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