Skill

bootstrap5-ui

Production-grade Bootstrap 5.3 patterns for building modern, responsive web UIs in HTML and ASP.NET Core Razor Pages/Views. Use when creating or styling web pages, layouts, navigation, forms, cards, modals, tables, or any UI component with Bootstrap 5. Covers the grid system, responsive breakpoints, utility classes, color modes (dark/light), accessibility, and integration with ASP.NET Core tag helpers and Razor syntax. Trigger on any task involving Bootstrap CSS classes, responsive HTML layouts, Razor Page UI design, or front-end styling for .NET web applications.

Install

npx claudepluginhub wshaddix/dotnet-skills

Tool Access

This skill uses the workspace's default tool permissions.

Supporting Assets

references/components.mdreferences/razor-integration.md

SKILL.md

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Last CommitFeb 12, 2026

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Bootstrap 5 UI

Production patterns for building responsive, accessible web UIs with Bootstrap 5.3 in HTML and ASP.NET Core Razor Pages/Views. Target Bootstrap 5.3.x (current CDN: 5.3.8). Bootstrap 5 dropped jQuery dependency entirely.

Setup in ASP.NET Core

CDN (Quick Start)

In _Layout.cshtml or _Host.cshtml:

<!-- In <head> -->
<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.8/dist/css/bootstrap.min.css"
      rel="stylesheet"
      integrity="sha384-sRIl4kxILFvY47J16cr9ZwB07vP4J8+LH7qKQnuqkuIAvNWLzeN8tE5YBujZqJLB"
      crossorigin="anonymous">

<!-- Before closing </body> -->
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.8/dist/js/bootstrap.bundle.min.js"
        integrity="sha384-FKyoEForCGlyvwx9Hj09JcYn3nv7wiPVlz7YYwJrWVcXK/BmnVDxM+D2scQbITxI"
        crossorigin="anonymous"></script>

LibMan (Recommended for Production)

// libman.json
{
  "version": "1.0",
  "defaultProvider": "jsdelivr",
  "libraries": [
    {
      "library": "bootstrap@5.3.8",
      "destination": "wwwroot/lib/bootstrap/"
    }
  ]
}

Reference locally in layout:

<link rel="stylesheet" href="~/lib/bootstrap/dist/css/bootstrap.min.css" />
<script src="~/lib/bootstrap/dist/js/bootstrap.bundle.min.js"></script>

Required Globals

Always include in <head>:

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">

Grid System

Bootstrap uses a 12-column flexbox grid with 6 responsive breakpoints:

Breakpoint	Prefix	Min-width
Extra small	`.col-`	<576px
Small	`.col-sm-`	>=576px
Medium	`.col-md-`	>=768px
Large	`.col-lg-`	>=992px
Extra large	`.col-xl-`	>=1200px
XXL	`.col-xxl-`	>=1400px

Core Pattern

<div class="container">
  <div class="row">
    <div class="col-md-8">Main content</div>
    <div class="col-md-4">Sidebar</div>
  </div>
</div>

Key Rules

Always wrap columns in .row inside a .container (or .container-fluid for full-width)
Columns must be direct children of rows
Use .g-* classes for gutters (.g-0 removes gutters, .gx-* horizontal, .gy-* vertical)
Use .row-cols-* on the row for uniform column counts: <div class="row row-cols-1 row-cols-md-3 g-4">
Mix breakpoints: <div class="col-6 col-md-4 col-lg-3"> — stacks to 2-up on xs, 3-up on md, 4-up on lg

Container Types

.container — responsive fixed-width
.container-fluid — full-width always
.container-{breakpoint} — fluid until breakpoint, then fixed

Spacing Utilities

Format: {property}{sides}-{breakpoint}-{size}

Property: m (margin), p (padding) Sides: t top, b bottom, s start(left), e end(right), x horizontal, y vertical, blank = all Size: 0=0, 1=0.25rem, 2=0.5rem, 3=1rem, 4=1.5rem, 5=3rem, auto

<div class="mt-3 mb-4 px-2">Spaced element</div>
<div class="mx-auto" style="width: 200px;">Centered block</div>
<div class="py-md-5">Padding only on md+</div>

Color Modes (Dark/Light)

Bootstrap 5.3 supports data-bs-theme attribute for dark mode:

<!-- Global dark mode -->
<html lang="en" data-bs-theme="dark">

<!-- Per-component -->
<div class="card" data-bs-theme="dark">...</div>
<nav class="navbar bg-dark" data-bs-theme="dark">...</nav>

Use semantic color classes that adapt to color mode:

bg-body, bg-body-secondary, bg-body-tertiary — adapt to theme
text-body, text-body-secondary, text-body-emphasis — adapt to theme
border-body — adapts to theme

Avoid hardcoded colors. Use bg-body-tertiary instead of bg-light for theme-aware backgrounds.

Common Component Patterns

Navbar

<nav class="navbar navbar-expand-lg bg-body-tertiary">
  <div class="container-fluid">
    <a class="navbar-brand" href="#">Brand</a>
    <button class="navbar-toggler" type="button"
            data-bs-toggle="collapse" data-bs-target="#mainNav"
            aria-controls="mainNav" aria-expanded="false"
            aria-label="Toggle navigation">
      <span class="navbar-toggler-icon"></span>
    </button>
    <div class="collapse navbar-collapse" id="mainNav">
      <ul class="navbar-nav me-auto mb-2 mb-lg-0">
        <li class="nav-item">
          <a class="nav-link active" aria-current="page" href="#">Home</a>
        </li>
        <li class="nav-item">
          <a class="nav-link" href="#">About</a>
        </li>
      </ul>
    </div>
  </div>
</nav>

Cards in Grid

<div class="row row-cols-1 row-cols-md-2 row-cols-lg-3 g-4">
  <div class="col">
    <div class="card h-100">
      <img src="..." class="card-img-top" alt="...">
      <div class="card-body">
        <h5 class="card-title">Title</h5>
        <p class="card-text">Description text.</p>
        <a href="#" class="btn btn-primary">Action</a>
      </div>
    </div>
  </div>
  <!-- repeat -->
</div>

Forms

<form method="post">
  <div class="mb-3">
    <label for="email" class="form-label">Email</label>
    <input type="email" class="form-control" id="email">
  </div>
  <div class="mb-3">
    <label for="password" class="form-label">Password</label>
    <input type="password" class="form-control" id="password">
  </div>
  <div class="mb-3 form-check">
    <input type="checkbox" class="form-check-input" id="remember">
    <label class="form-check-label" for="remember">Remember me</label>
  </div>
  <button type="submit" class="btn btn-primary">Sign in</button>
</form>

Floating Labels

<div class="form-floating mb-3">
  <input type="email" class="form-control" id="floatEmail" placeholder="name@example.com">
  <label for="floatEmail">Email address</label>
</div>

Responsive Table

<div class="table-responsive">
  <table class="table table-striped table-hover">
    <thead class="table-dark">
      <tr><th>Name</th><th>Email</th><th>Actions</th></tr>
    </thead>
    <tbody>
      <tr><td>John</td><td>john@example.com</td><td><a class="btn btn-sm btn-outline-primary">Edit</a></td></tr>
    </tbody>
  </table>
</div>

Razor Pages Integration

For detailed ASP.NET Core Razor Pages integration patterns including tag helpers, validation, layouts, and partial views, see references/razor-integration.md.

Key points:

Use asp-for, asp-page, asp-action tag helpers with Bootstrap classes
Combine asp-validation-for with .invalid-feedback / .is-invalid classes
Place Bootstrap validation classes via jQuery Validation Unobtrusive or custom JS
Use @section Scripts for page-specific scripts in layout

Component Reference

For complete component patterns (modals, alerts, toasts, accordion, pagination, breadcrumbs, badges, offcanvas, spinners, progress bars), see references/components.md.

Utility Classes Quick Reference

Display

d-none, d-block, d-flex, d-grid, d-inline, d-inline-block Responsive: d-md-none, d-lg-flex

Flexbox

justify-content-{start|center|end|between|around|evenly} align-items-{start|center|end|stretch} flex-{row|column}, flex-wrap, flex-grow-1

Text

text-{start|center|end}, text-{lowercase|uppercase|capitalize} fw-{bold|semibold|normal|light}, fs-{1-6} text-truncate, text-nowrap, text-break

Colors

text-{primary|secondary|success|danger|warning|info|light|dark} bg-{primary|secondary|success|danger|warning|info|light|dark} text-bg-{color} — sets matching text+bg together

Borders & Shadows

border, border-{top|bottom|start|end}, border-{color}, border-{1-5} rounded, rounded-{0-5|circle|pill} shadow, shadow-sm, shadow-lg, shadow-none

Sizing

w-{25|50|75|100|auto}, h-{25|50|75|100|auto} mw-100, mh-100, vw-100, vh-100 min-vw-100, min-vh-100

Position

position-{static|relative|absolute|fixed|sticky} top-{0|50|100}, start-{0|50|100}, translate-middle

Accessibility Requirements

Always include aria-label on icon-only buttons and togglers
Use aria-current="page" on active nav links
Use aria-expanded on collapse/dropdown triggers
Provide alt text on images; use .visually-hidden for screen-reader-only text
Ensure color contrast meets WCAG 2.1 AA (4.5:1 for text, 3:1 for large text)
Use semantic HTML: <nav>, <main>, <header>, <footer>, <section>, <article>
Never remove :focus styles; use Bootstrap's .focus-ring utility for custom focus

Anti-Patterns

Using col-* without a parent .row — breaks grid alignment
Nesting containers — only nest rows, never containers inside containers
Using <br> and inline styles for spacing — use spacing utilities (mt-3, mb-4)
Hardcoding bg-light/bg-dark — use bg-body-tertiary for theme-aware backgrounds
Forgetting navbar-expand-{breakpoint} — navbar won't collapse responsively
Mixing Bootstrap 4 classes (e.g., ml-3, mr-3) — use ms-3, me-3 (start/end logical properties)
Omitting type="button" on non-submit buttons in forms — causes unintended form submission
Using <a> for actions without href — use <button> for actions, <a> for navigation
Skipping .form-label on form inputs — hurts accessibility
Not wrapping tables in .table-responsive — causes horizontal overflow on mobile