The alt attribute specifies an alternate text for an image, if the image cannot be displayed. If a user, for some reason, cannot view an image (because of slow connection, an error in the src attribute, or the user is using a screen reader), then browsers will display alternative information to replace the image:
| HTML file: | Displayed by browser: |
|---|---|
|
<!DOCTYPE html>
<html> <body> <p>If a browser cannot find an image, it will display the alternate text:</p> <img src="wrongname.gif" alt="HTML5 Icon" style="width:128px;height:128px;"> </body> </html> |
If a browser cannot find an image, it will display the alternate text: 
|
The alt attribute is required. A web page will not validate correctly without it.
