Ev Onblur

## HTML onblur Event Attribute The `onblur` event attribute fires when an HTML element loses focus. It is most commonly used on form elements (such as ``, `

`) to perform validation, formatting, or auto-saving when a user moves away from an input field.

The opposite of the `onblur` attribute is the [`onfocus`](ev-onfocus.html) attribute, which triggers when an element gains focus.

---

## Browser Support

The `onblur` event attribute is a standard feature and is fully supported by all modern web browsers:

* Google Chrome
* Mozilla Firefox
* Microsoft Edge / Internet Explorer
* Safari
* Opera

---

## Syntax

You can define the `onblur` attribute inline within an HTML element:

```html
<element onblur="script">
```

### Attribute Values

---

## HTML 4.01 vs. HTML5

There are no differences in the behavior or support of the `onblur` attribute between HTML 4.01 and HTML5.

---

## Code Examples

### Example 1: Inline Validation and Formatting
In this example, when the user leaves the input field, the `onblur` event triggers a JavaScript function that converts the entered text to uppercase.

```html
<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>onblur Event Example</title>
 
</head>
<body>

Enter your name and click outside the input field to trigger the onblur event:
 <input type="text" name="fname" id="fname" onblur="convertToUpperCase()">

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

</body>
</html>
```

### Example 2: Using JavaScript Event Listeners (Recommended)
For cleaner, more maintainable code, it is best practice to separate your HTML structure from your JavaScript behavior using `addEventListener`:

```html
<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>onblur Event Listener Example</title>
</head>
<body>

<label for="email">Email Address:</label>
 <input type="email" id="email" placeholder="user@example.com">
 Please enter a valid email address.

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

</body>
</html>
```

---

## Considerations and Best Practices

1. **Event Bubbling vs. Capturing**: The `blur` event **does not bubble** up the DOM tree. If you need to detect focus loss on a parent element for its child elements (event delegation), you should use the `focusout` event instead, which does bubble.
2. **Accessibility (a11y)**: Avoid using `onblur` to force focus back onto an element (e.g., creating an infinite loop where a user cannot leave an invalid field). This can trap keyboard-only users and screen readers, severely degrading the user experience. Instead, display a clear, non-intrusive error message.
3. **Performance**: If you are performing heavy operations (like making an API request to validate a username) on `onblur`, ensure you handle loading states gracefully so the UI remains responsive.</div><div class="post-nav"><a href="/post/ev-onchange.html">← Ev Onchange</a><a href="/post/ev-onunload.html">Ev Onunload →</a></div></div>
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