Sel Required

## CSS :required Pseudo-class Selector The `:required` pseudo-class selector in CSS is used to target and style form elements that have the HTML `required` attribute set. This allows developers to visually distinguish mandatory fields from optional ones, improving the user experience (UX) during form completion. --- ## Definition and Usage The `:required` selector matches any form element that must be filled out before the form can be submitted. * **Target Elements:** This selector is only applicable to form elements that support the `required` attribute, specifically: * `` * `

By applying styles with `:required`, you can automatically highlight mandatory fields (e.g., adding a red border, a specific background color, or an indicator icon) without needing to manually add custom utility classes like `.is-required` in your HTML.

---

## Syntax

```css
:required {
  /* CSS declarations */
}
```

You can also chain it with specific element selectors for more targeted styling:

```css
input:required {
  background-color: #fff9e6;
}

textarea:required {
  border: 2px solid #ff4d4f;
}
```

---

## Code Examples

### Example 1: Basic Usage (Highlighting Required Inputs)
In this example, any `<input>` element with the `required` attribute will have a light yellow background.

```html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>CSS :required Selector Example</title>

</head>
<body>

<form>
 <label for="username">Username (Required):</label>
 <input type="text" id="username" name="username" required>
 
 
 <label for="nickname">Nickname (Optional):</label>
 <input type="text" id="nickname" name="nickname">
 
 
 <input type="submit" value="Submit">
</form>

<script>
 // Placeholder for Google Analytics
</script>

</body>
</html>
```

### Example 2: Advanced Form Styling with `:required` and `:optional`
You can combine `:required` with the `:optional` pseudo-class to create a clear visual distinction between mandatory and non-mandatory fields.

```css
/* Style required inputs with a red left border */
input:required, textarea:required {
  border-left: 4px solid #ff4d4f;
  background-color: #fffbfb;
}

/* Style optional inputs with a gray left border */
input:optional, textarea:optional {
  border-left: 4px solid #ccc;
  background-color: #fafafa;
}
```

---

## Browser Support

The `:required` pseudo-class is widely supported across all modern browsers.

| Selector | Chrome | Edge / IE | Firefox | Safari | Opera |
| :--- | :--- | :--- | :--- | :--- | :--- |
| **:required** | 10.0+ | 10.0+ | 4.0+ | 5.0+ | 10.0+ |

---

## Key Considerations

1. **Accessibility (a11y):** While visual styling helps sighted users identify required fields, you should always pair CSS styling with proper HTML attributes (like `required` and `aria-required="true"`) and clear text labels (e.g., adding `*` or `(required)`) to ensure screen readers can convey this information to visually impaired users.
2. **Dynamic Validation:** The `:required` state is static based on the presence of the HTML attribute. If you want to style elements based on whether their current input is valid or invalid, combine it with the `:valid` or `:invalid` pseudo-classes (e.g., `input:required:invalid`).

---

## Related Pages

* [CSS :optional Selector](./sel-optional.html) - Targets form elements that do not have the `required` attribute.
* [CSS :valid Selector](./sel-valid.html) - Targets form elements with values that validate successfully.
* [CSS :invalid Selector](./sel-invalid.html) - Targets form elements with values that do not validate successfully.</div><div class="post-nav"><a href="/post/sel-optional.html">← Sel Optional</a><a href="/post/sel-read-write.html">Sel Read Write →</a></div></div>
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