Glossary Term

Alt Text and Alt Tags

Also known as Alternative text, Image Alt Text, Alt Attribute, Alt Description, this is the text added to an image’s HTML that describes what the image shows. Alt text and alt tags are different things, but serve the same overall purpose.

What it means

Alt tags and alt text are often used interchangeably, but they aren’t the same thing.

An alt tag is the HTML attribute added to an image element, written as alt=”” in the image’s code. The technically correct term is alt attribute, but “alt tag” is commonly used in SEO and web development.

Alt text (short for alternative text) is the description inside that attribute. It describes the image for anyone using a screen reader or assitive technologies, displays if the image fails to load, and gives search engines context about visual content.

Every image should include an alt attribute. Alt text is a fundamental part of web accessibility because it helps users of screen readers and other assistive technologies understand visual content. Purely decorative images, such as background patterns, dividers, or visual flourishes, should use an empty attribute (alt=””) so assistive technologies skip them rather than announcing unnecessary information.

Alt text also helps search engines understand images and how they relate to the surrounding content. It isn’t a major ranking factor on its own, but it can improve image search visibility and support AI-powered and visual search systems.

Tips for Writing Effective Alt Text

Describe what the image shows and why it matters on the page.
Keep it concise, ideally 125 characters or fewer.
Skip phrases like “image of” or “picture of,” since screen readers already identify images.
For linked images or buttons, describe the action or destination, not the graphic.
Use keywords only when they naturally describe the image, and never stuff them in

Why it matters

Alt tags improve accessibility, help search engines understand visual content, and can increase visibility in image search results. Well-written alt text also creates a better experience for users who cannot view images.

Example

An online bakery uploads a photo of a chocolate birthday cake and uses the alt tag: "Custom chocolate birthday cake with vanilla frosting." This helps both search engines and screen readers understand the image.

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