Bootstrap 入门

Bootstrap is a powerful, feature-packed frontend toolkit. Build anything—from prototype to production—in minutes.

On this page

Quick start

Get started by including Bootstrap’s production-ready CSS and JavaScript via CDN without the need for any build steps. See it in practice with this Bootstrap CodePen demo.

Create a new index.html file in your project root. Include the <meta name="viewport"> tag as well for proper responsive behavior in mobile devices.

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Bootstrap demo</title>
  </head>
  <body>
    <h1>Hello, world!</h1>
  </body>
</html>

Include Bootstrap’s CSS and JS. Place the <link> tag in the <head> for our CSS, and the <script> tag for our JavaScript bundle (including Popper for positioning dropdowns, poppers, and tooltips) before the closing </body>. Learn more about our CDN links.

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Bootstrap demo</title>
    <link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-GLhlTQ8iRABdZLl6O3oVMWSktQOp6b7In1Zl3/Jr59b6EGGoI1aFkw7cmDA6j6gD" crossorigin="anonymous">
  </head>
  <body>
    <h1>Hello, world!</h1>
    <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.bundle.min.js" integrity="sha384-/mhDoLbDldZc3qpsJHpLogda//BVZbgYuw6kof4u2FrCedxOtgRZDTHgHUhOCVim" crossorigin="anonymous"></script>
  </body>
</html>

You can also include Popper and our JS separately. If you don’t plan to use dropdowns, popovers, or tooltips, save some kilobytes by not including Popper.

<script src="https://cdn.jsdelivr.net/npm/@popperjs/[email protected]/dist/umd/popper.min.js" integrity="sha384-oBqDVmMz9ATKxIep9tiCxS/Z9fNfEXiDAYTujMAeBAsjFuCZSmKbSSUnQlmh/jp3" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.min.js" integrity="sha384-ep+dxp/oz2RKF89ALMPGc7Z89QFa32C8Uv1A3TcEK8sMzXVysblLA3+eJWTzPJzT" crossorigin="anonymous"></script>

Hello, world! Open the page in your browser of choice to see your Bootstrapped page. Now you can start building with Bootstrap by creating your own layout, adding dozens of components, and utilizing our official examples.

CDN links

As reference, here are our primary CDN links.

Description	URL
CSS	`https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css`
JS	`https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.bundle.min.js`

You can also use the CDN to fetch any of our additional builds listed in the Contents page.

Next steps

Read a bit more about some important global environment settings that Bootstrap utilizes.
Read about what’s included in Bootstrap in our contents section and the list of components that require JavaScript below.
Need a little more power? Consider building with Bootstrap by including the source files via package manager.
Looking to use Bootstrap as a module with <script type="module">? Please refer to our using Bootstrap as a module section.

JS components

Curious which components explicitly require our JavaScript and Popper? Click the show components link below. If you’re at all unsure about the general page structure, keep reading for an example page template.

Show components requiring JavaScript

Alerts for dismissing
Buttons for toggling states and checkbox/radio functionality
Carousel for all slide behaviors, controls, and indicators
Collapse for toggling visibility of content
Dropdowns for displaying and positioning (also requires Popper)
Modals for displaying, positioning, and scroll behavior
Navbar for extending our Collapse and Offcanvas plugins to implement responsive behaviors
Navs with the Tab plugin for toggling content panes
Offcanvases for displaying, positioning, and scroll behavior
Scrollspy for scroll behavior and navigation updates
Toasts for displaying and dismissing
Tooltips and popovers for displaying and positioning (also requires Popper)

Important globals

Bootstrap employs a handful of important global styles and settings, all of which are almost exclusively geared towards the normalization of cross browser styles. Let’s dive in.

HTML5 doctype

Bootstrap requires the use of the HTML5 doctype. Without it, you’ll see some funky and incomplete styling.

<!doctype html>
<html lang="en">
  ...
</html>

Responsive meta tag

Bootstrap is developed mobile first, a strategy in which we optimize code for mobile devices first and then scale up components as necessary using CSS media queries. To ensure proper rendering and touch zooming for all devices, add the responsive viewport meta tag to your <head>.

<meta name="viewport" content="width=device-width, initial-scale=1">

You can see an example of this in action in the quick start.

Box-sizing

For more straightforward sizing in CSS, we switch the global box-sizing value from content-box to border-box. This ensures padding does not affect the final computed width of an element, but it can cause problems with some third-party software like Google Maps and Google Custom Search Engine.

On the rare occasion you need to override it, use something like the following:

.selector-for-some-widget {
  box-sizing: content-box;
}

With the above snippet, nested elements—including generated content via ::before and ::after—will all inherit the specified box-sizing for that .selector-for-some-widget.

Learn more about box model and sizing at CSS Tricks.

Reboot

For improved cross-browser rendering, we use Reboot to correct inconsistencies across browsers and devices while providing slightly more opinionated resets to common HTML elements.

Community

Stay up-to-date on the development of Bootstrap and reach out to the community with these helpful resources.

Read and subscribe to The Official Bootstrap Blog.
Ask and explore our GitHub Discussions.
Chat with fellow Bootstrappers in IRC. On the irc.libera.chat server, in the #bootstrap channel.
Implementation help may be found at Stack Overflow (tagged bootstrap-5).
Developers should use the keyword bootstrap on packages that modify or add to the functionality of Bootstrap when distributing through npm or similar delivery mechanisms for maximum discoverability.

You can also follow @getbootstrap on Twitter for the latest gossip and awesome music videos.