Bootstrap
The original class-based CSS framework.
Bootstrap remains the fastest way to get a conventional, responsive interface with no build step and no framework. At around 175,000 stars it is the most starred project in this directory by a wide margin, and it is still the default in a great deal of server-rendered software.
At a glance
| Install | one <link> tag, or npm install bootstrap |
| Build step | optional, works from a CDN |
| Styling | Sass variables, plus CSS custom properties since v5 |
| JavaScript | vanilla plugins, no framework dependency |
| MCP server | not published |
| License | MIT |
Install
No tooling required:
<link href="https://cdn.jsdelivr.net/npm/bootstrap@5/dist/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5/dist/js/bootstrap.bundle.min.js"></script>
Customise before you override
The mistake most teams make is fighting Bootstrap with !important. Import the Sass source and set variables first, and the whole system follows:
$primary: #339999;
$border-radius: 0.5rem;
$font-family-base: "Inter", sans-serif;
@import "bootstrap/scss/bootstrap";
<button class="btn btn-primary">Save changes</button>
<div class="card"><div class="card-body">…</div></div>
Choose it if
- You are working in Rails, Django, Laravel, PHP or any server-rendered stack.
- You need something live this afternoon with no npm involved.
- You are handing the project to a team that will recognise every class name.
Look elsewhere if
- Visual distinctiveness matters. Unmodified Bootstrap is instantly recognisable, and products using it look related.
- You want documented WAI-ARIA conformance per component rather than general accessibility guidance.