HTML alt Attribute: Reference and Examples

The alt attribute is a small instruction attached to an HTML element. Its job is to text alternative for an image. It is easier to remember when you can see it in a real piece of markup.

What alt is used for

Text alternative for an image. The attribute appears inside an element’s opening tag. Depending on its definition, it may take a specific string, a number, an enumerated keyword, or be a boolean attribute.

The example below uses it in a img context. Other elements may support it too, or may give the same attribute a different meaning.

Example you can try

<figure>
    <img src="photo.jpg" alt="A child reading a book" width="600" height="400">
    <figcaption>Mountain trail</figcaption>
</figure>

How the example works

Look for alt in the snippet. Here the example shows the value A child reading a book. This is a concrete input the browser can interpret; it is not just text shown to the reader.

Describe an informative image’s function or content. Use alt="" for genuinely decorative images.

Values and important behavior

Use the value format shown by the HTML definition. Do not assume that a value accepted in one attribute also works in another. When a browser ignores an invalid value, inspect the element and correct the markup.

This detail matters most when the page receives user input, navigates to another document, or loads an external resource. In those cases, check the browser behavior and any server-side requirements separately.

Small practice task

Copy the code and change alt to another sensible value, or remove it entirely if it is optional. Test the difference in the browser and inspect any submitted value or network request.

Common Beginner Mistakes

• Describe an informative image’s function or content. Use alt="" for genuinely decorative images.
• Using alt on an element that does not support it.
• Believing that an HTML hint or client-side check replaces real server validation or a security policy.

Key Takeaways

• alt is used to text alternative for an image.
• Describe an informative image’s function or content. Use alt="" for genuinely decorative images.
• Choose valid values and test the result instead of guessing what the browser will do.