This snippet transforms a standard HTML checkbox into a sleek, modern toggle switch. Relying entirely on CSS pseudo-elements and the :checked state, it delivers incredibly smooth animations without a single line of JavaScript.

Code

<label class="custom-toggle">
  <input type="checkbox" class="custom-toggle-input" aria-label="Toggle Switch" />
  <span class="custom-toggle-slider"></span>
</label>

/* Toggle switch container */
.custom-toggle {
  position: relative;
  display: inline-block;
  width: 60px;
  height: 34px;
}

/* Hide the default checkbox */
.custom-toggle-input {
  opacity: 0;
  width: 0;
  height: 0;
}

/* Slider background */
.custom-toggle-slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: #e2e8f0;
  transition: background-color 0.4s;
  border-radius: 34px;
  box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.1);
}

/* Slider thumb */
.custom-toggle-slider:before {
  position: absolute;
  content: "";
  height: 26px;
  width: 26px;
  left: 4px;
  bottom: 4px;
  background-color: white;
  transition: transform 0.4s cubic-bezier(0.68, -0.55, 0.265, 1.55);
  border-radius: 50%;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

/* Background color when checked */
.custom-toggle-input:checked + .custom-toggle-slider {
  background-color: #3b82f6;
}

/* Outline on keyboard focus */
.custom-toggle-input:focus-visible + .custom-toggle-slider {
  outline: 2px solid #3b82f6;
  outline-offset: 2px;
}

/* Thumb movement when checked */
.custom-toggle-input:checked + .custom-toggle-slider:before {
  transform: translateX(26px);
}

Implementation Points

Native <input type="checkbox"> elements suffer from inconsistent cross-browser styling and limited customization. This snippet elegantly solves this by visually hiding the default checkbox—while retaining its native functionality—and constructing a custom UI using an adjacent <span> element as the slider.

1. Hiding the Native Input: Setting opacity: 0 alongside zero width and height completely removes the default checkbox from view while keeping it fully functional and accessible in the DOM.
2. Styling the Slider: The circular toggle “thumb” is efficiently rendered using the ::before pseudo-element.
3. Fluid Animation: Applying a custom easing curve (transition: transform 0.4s cubic-bezier(0.68, -0.55, 0.265, 1.55)) gives the thumb a highly satisfying, slightly bouncy physics effect when toggled.
4. Accessibility (a11y): Focus states are explicitly handled using :focus-visible, ensuring that the custom switch receives a clear, distinct outline during keyboard navigation.

This toggle switch is highly versatile and perfect for interfaces requiring intuitive binary choices, such as application settings panels or dark mode toggles.