cannot select multiple files when uploading

I am making an app using HTML CSS and JS by watching a tutorial, the app will merge multiple pdfs but I can’t select multiple files I even tried to can the type (when selecting files) to all but it doesn’t work

My Code:

<div class="container">
    <h1>PDF MERGER TOOL</h1>
    <form method="post" action="/merge" enctype='multipart/form-data'>
        <div class="form-group">
          <label for="exampleFormControlFile1">Select the PDF files you want to merge</label>
          <input type="file" class="form-control-file" name="pdfs" id="exampleFormControlFile1" accept=".PDF">
          <input type="submit" value="Submit" class="btn btn-primary my-4">
        </div>
      </form>
</div>

>Solution :

You need to add the multiple attribute to enable multiple files selection.

<input type="file" class="form-control-file" name="pdfs" id="exampleFormControlFile1" accept=".PDF" multiple>