Load Bootstrap modal on page load without firing button or using jQuery

Question 1

Create a CSS class for .modal and add display:block. Also give in class to modal div.

CSS

.modal {
  display:block;
}

HTML

<div id="my-modal" class="modal fade in">

Edit: Somehow default closing function will not work, you will need to add custom script for that.

Question 2

I spent some time trying to accommodate this and found that this worked fine for my needs which incorporated a single login page... Obviously this is not the finished article but an excellent base from which I was able to start with. Hope it is of some use to someone...

<body style="background: #555;">
    <!-- Modal -->
    <div class="modal-dialog" style="margin-top: 20%;">
        <div class="modal-content">
            <div class="modal-header">
                <button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>
                <h4 class="modal-title">Modal title</h4>
            </div>
            <div class="modal-body">
                <p>One fine body…</p>
            </div>
            <div class="modal-footer">
                <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
                <button type="button" class="btn btn-primary">Save changes</button>
            </div>
        </div><!-- /.modal-content -->
    </div>
</body>

Question 3

On Bootstrap 5, just create a modal variable with options and runs it with .show()

var myModal = new bootstrap.Modal(document.getElementById('modal'), {keyboard: false, backdrop: 'static'});
myModal.show();

Without Jquery, you cannot use this;

myModal.modal('show');

Question 4

You could utilize the page onload function

<link rel="stylesheet" href="https://netdna.bootstrapcdn.com/bootstrap/3.0.3/css/bootstrap.min.css">
<link rel="stylesheet" href="https://netdna.bootstrapcdn.com/bootstrap/3.0.3/css/bootstrap-theme.min.css">
<script src="https://code.jquery.com/jquery-1.10.2.min.js"></script>
<script src="https://netdna.bootstrapcdn.com/bootstrap/3.0.3/js/bootstrap.min.js"></script>

<body onLoad="$('#my-modal').modal('show');">
    <div id="my-modal" class="modal fade">
        <div class="modal-dialog">
            <div class="modal-content">
                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
                <h4 class="modal-title">Title</h4>
                </div>
                <div class="modal-body">
                    Hello World!
                </div>
            </div>
        </div> 
    </div>
</body>

Question 5

On Bootstrap 4 --

Add the show class to your modal

<div class="modal fade show" id="exampleModal" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true">

and following css --

.modal {
    display:block;
  }

Question 6

On bootstrap 5 and don't use Jquery here my answer;

First we assign an id to the button, select to button and then when page load click automatically this button.

document.getElementById("btn-my").click();

and in css;

#btn-my {
display: none;
}

That's it.

Question 7

<div id="modal1" class="modal" data-show role="dialog">

data-show help you

Load Bootstrap modal on page load without firing button or using jQuery

Demo: Fiddle