1, download the installation file to a server
Bootstrap v4 Download (compressed packet includes bootstrap.min.css and bootstrap.min.js)
https://getbootstrap.com/docs/4.3/getting-started/download/
jquery.min.js Download
https://cdn.staticfile.org/jquery/3.4.1/jquery.min.js
popper.min.js Download
https://cdn.staticfile.org/popper.js/1.15.0/umd/popper.min.js
2, the use of Bootstrap 4 CDN
Domestic recommend the use of libraries on the CDN StaticFile:
Bootstrap4 CDN
<!-- 新 Bootstrap4 核心 CSS 文件 -->
<link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/4.1.0/css/bootstrap.min.css">
<!-- jQuery文件。务必在bootstrap.min.js 之前引入 -->
<script src="https://cdn.staticfile.org/jquery/3.2.1/jquery.min.js"></script>
<!-- popper.min.js 用于弹窗、提示、下拉菜单 -->
<script src="https://cdn.staticfile.org/popper.js/1.12.5/umd/popper.min.js"></script>
<!-- 最新的 Bootstrap4 核心 JavaScript 文件 -->
<script src="https://cdn.staticfile.org/twitter-bootstrap/4.1.0/js/bootstrap.min.js"></script>
In addition, you can also use the following CDN services:
国内推荐使用 : https://www.staticfile.org/
国际推荐使用：https://cdnjs.com/