Cách tạo form inline responsive với CSS

Giới thiệu

Inline form (form nội tuyến) hiển thị label, input, button trên một hàng ngang. Responsive: trên desktop nằm ngang, trên mobile xếp dọc (stack). Dùng Flexbox + media query.

Ví dụ hoàn chỉnh - Inline Login Form

<!DOCTYPE html>
<html lang="vi">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Responsive Inline Form</title>
  <style>
    * { box-sizing: border-box; }
    body { font-family: 'Segoe UI', system-ui, sans-serif; background: #f5f5f5; padding: 40px 20px; }
    .form-card { max-width: 700px; margin: 0 auto; background: #fff; padding: 32px; border-radius: 16px; box-shadow: 0 4px 24px rgba(0,0,0,0.08); }
    h1 { text-align: center; margin: 0 0 24px; font-size: 24px; }
    .inline-form {
      display: flex;
      flex-wrap: wrap;
      align-items: flex-end; /* Căn đáy: label, input, button cùng baseline */
      gap: 16px;
    }
    .form-group { display: flex; flex-direction: column; gap: 6px; flex: 1; min-width: 180px; }
    .form-group label { font-size: 13px; font-weight: 500; color: #333; white-space: nowrap; }
    .form-group input {
      padding: 12px 14px;
      font-size: 15px;
      border: 1.5px solid #e0e0e0;
      border-radius: 8px;
      transition: border-color 0.2s, box-shadow 0.2s;
    }
    .form-group input:focus { outline: none; border-color: #667eea; box-shadow: 0 0 0 3px rgba(102,126,234,0.15); }
    .btn-submit {
      padding: 12px 24px;
      font-size: 15px;
      font-weight: 600;
      color: #fff;
      background: #667eea;
      border: none;
      border-radius: 8px;
      cursor: pointer;
      white-space: nowrap;
      transition: background 0.2s, transform 0.1s;
    }
    .btn-submit:hover { background: #5a6fd6; }
    .btn-submit:active { transform: scale(0.98); }
    /* Mobile: stacked */
    @media (max-width: 600px) {
      .inline-form { flex-direction: column; align-items: stretch; }
      .form-group { width: 100%; }
      .btn-submit { width: 100%; }
    }
  </style>
</head>
<body>
  <div class="form-card">
    <h1>Inline Login Form</h1>
    <form class="inline-form">
      <div class="form-group">
        <label for="email">Email</label>
        <input type="email" id="email" name="email" placeholder="you@example.com" required autocomplete="email">
      </div>
      <div class="form-group">
        <label for="password">Mật khẩu</label>
        <input type="password" id="password" name="password" placeholder="••••••••" required autocomplete="current-password">
      </div>
      <button type="submit" class="btn-submit">Đăng nhập</button>
    </form>
  </div>
</body>
</html>

Kỹ thuật Flexbox cốt lõi

• display: flex; flex-wrap: wrap: Cho phép xuống dòng khi hẹp.
• align-items: flex-end: Căn đáy label/input/button - quan trọng cho visual alignment.
• gap: 16px: Khoảng cách đều, không cần margin phức tạp.
• flex: 1; min-width: 180px: Input co giãn, tối thiểu 180px trước khi wrap.

.filter-bar {
  display: flex; flex-wrap: wrap; gap: 12px; align-items: flex-end;
  padding: 20px; background: #fff; border-radius: 12px; margin-bottom: 24px;
}
.filter-group { flex: 1; min-width: 150px; }
.filter-group select { padding: 10px 12px; border: 1px solid #ddd; border-radius: 6px; }
@media (max-width: 640px) { .filter-bar { flex-direction: column; align-items: stretch; } }

.nav-form { display: flex; align-items: center; gap: 8px; }
.nav-form label { margin: 0; font-size: 13px; white-space: nowrap; }
.nav-form input { padding: 8px 12px; font-size: 13px; width: 180px; }
.nav-form button { padding: 8px 16px; font-size: 13px; white-space: nowrap; }
@media (max-width: 768px) {
  .nav-form { flex-direction: column; width: 100%; margin-top: 12px; }
  .nav-form input { width: 100%; }
}