BootStrap

Koustav MoitraKoustav Moitra
3 min read

What is Bootstrap?

  • Bootstrap is a free and open-source CSS framework.

  • Used to build responsive and mobile-first websites quickly.

  • Provides pre-styled components, layout grid, and utility classes.

Getting Started with Bootstrap 5.3

Using CDN:

<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/js/bootstrap.bundle.min.js"></script>

Starter Template:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>Bootstrap Page</title>
  <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css" rel="stylesheet" />
</head>
<body>

  <h1 class="text-center mt-4">Hello Bootstrap!</h1>

</body>
</html>

Layout System (Grid in Bootstrap)

  • Bootstrap uses a 12-column grid system.

  • Based on Flexbox.

🔹 Containers:

<div class="container">Standard Width</div>
<div class="container-fluid">Full Width</div>

🔹 Rows & Columns:

<div class="container">
  <div class="row">
    <div class="col-4">Column 1</div>
    <div class="col-4">Column 2</div>
    <div class="col-4">Column 3</div>
  </div>
</div>

Bootstrap 5.3 Breakpoints

Bootstrap uses breakpoints to make websites responsive — so they look good on all screen sizes.

Device SizeClass InfixScreen Width
📱 Extra Small(none)Less than 576px
📱 Smallsm576px and up
📱📱 Mediummd768px and up
💻 Largelg992px and up
🖥️ Extra Largexl1200px and up
🖥️📺 Extra Extra Largexxl1400px and up
 
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
        <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.7/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-LN+7fdVzj6u52u30Kp6M/trliBMCMKTyK833zpbD+pXdCLuTusPj697FH4R/5mcr" crossorigin="anonymous">

        <style>
            *{
                padding: 0;
                margin: 0;
                box-sizing: border-box;
            }
            .box {
              background-color: lightblue;
              padding: 20px;
              text-align: center;
              border: 2px dashed #007bff;
              margin-bottom: 20px;    
            }
        </style>
</head>
<body>

 <!-- Normal Container: fixed width based on screen size -->
  <div class="container">
    <div class="box">.container (Fixed Width)</div>
  </div>

  <!-- Fluid Container: always 100% width -->
  <div class="container-fluid">
    <div class="box">.container-fluid (Full Width)</div>
  </div>

  <!-- Responsive Container: 100% until breakpoint -->
  <div class="container-md">
    <div class="box">.container-md (100% width until "md", then fixed)</div>
  </div>



<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.7/dist/js/bootstrap.bundle.min.js" integrity="sha384-ndDqU0Gzau9qJ1lfW4pNLlhNTkCfHzAVBReH9diLvGRem5+R9g2FzA8ZGN954O5Q" crossorigin="anonymous"></script>

</body>
</html>
ClassBehavior
.containerFixed width depending on screen size (centered layout)
.container-fluidAlways full-width (100%) across all screen sizes
.container-mdFull-width below md breakpoint (768px), fixed-width above it

Components in Bootstrap

🔹 Buttons:

<button class="btn btn-primary">Primary</button>
<button class="btn btn-outline-success">Outline</button>

🔹 Navbar:

<nav class="navbar navbar-expand-lg navbar-light bg-light">
  <div class="container-fluid">
    <a class="navbar-brand" href="#">MySite</a>
    <button class="navbar-toggler" ... ></button>
    <div class="collapse navbar-collapse" id="navbarNav">
      <ul class="navbar-nav">
        <li class="nav-item"><a class="nav-link active" href="#">Home</a></li>
      </ul>
    </div>
  </div>
</nav>

🔹 Card:

<div class="card" style="width: 18rem;">
  <img src="..." class="card-img-top" alt="...">
  <div class="card-body">
    <h5 class="card-title">Title</h5>
    <p class="card-text">Some text.</p>
    <a href="#" class="btn btn-primary">Go</a>
  </div>
</div>

🔹 Form:

<form>
  <div class="mb-3">
    <label class="form-label">Email</label>
    <input type="email" class="form-control" />
  </div>
  <button class="btn btn-success">Submit</button>
</form>

🔹 Alerts:

<div class="alert alert-warning" role="alert">
  This is a warning alert!
</div>
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Koustav Moitra
Koustav Moitra