Add a scrollbar to a <textarea>

You will need to give your textarea a set height and then set overflow-y

textarea
{
resize: none;
overflow-y: scroll;
height:300px;
}

Try adding below CSS

textarea
{
    overflow-y:scroll;
}

What you need is overflow-y: scroll;

Demo

    textarea {
        overflow-y: scroll;
        height: 100px;
        resize: none; /* Remove this if you want the user to resize the textarea */
    }

<textarea></textarea>

textarea {
    overflow-y: scroll; /* Vertical scrollbar */
    overflow: scroll; /* Horizontal and vertical scrollbar*/
}