What is Alt Text?

Understanding Alt Text

Alt Text is an image attribute. It provides a written alternative to visual content. It helps screen readers explain images to people who are blind or have low vision. It can also show when an image fails to load. Its main purpose is accessibility, not visual display.

Related glossary terms: HTML, Page Experience.

A useful description explains the image’s role on the page. A product image may need the product name and an important feature. A chart may need its main finding. Decorative images add no information. They should generally have an empty alternative. This lets assistive technology skip them. Alt Text shouldn't repeat nearby text. It shouldn't begin with “image of” unless needed.

How Alt Text Works, Is Measured, or Is Used?

In HTML, Alt Text usually comes through the alt attribute on an image element. This element contains descriptive alternative text. A browser or assistive technology can access this text. This works when the visual file isn't available. It also helps users who rely on spoken output. Content management systems often provide an Alt Text field. The person entering the content remains responsible for its accuracy.

Writing Alt Text starts by identifying the image’s purpose. You should identify the information a reader needs. You should also review the surrounding content. A practical workflow asks whether the image is informative, functional, decorative, or text-based. Functional images should describe the action. Informative images should convey the key message. Decorative images should use an empty value. Images with essential text should provide that text accessibly.

• Informative image: describe the important subject or message.
• Functional image: describe the link or control outcome.
• Decorative image: use an empty Alt Text value.
• Complex graphic: provide a concise summary and nearby detailed explanation.

People usually evaluate Alt Text through review and accessibility testing. They don't use one universal score. Checks can include every meaningful image having an alternative. They can check whether wording fits the page context. They can check whether decorative images leave the reading order. Automated tools can detect missing attributes. They can't reliably judge whether a description is useful or accurate.

Why Alt Text Matters?

Effective Alt Text improves access to web content. It helps people using screen readers or browsing with images disabled. It also gives search engines extra text. This text can help them understand an image and its page relationship. Search visibility depends on many factors. These include page relevance, content quality, technical accessibility, and user experience.

Weak descriptions can cause confusion. They can repeat irrelevant keywords. They can hide information from users needing a text alternative. A vague description, such as “photo” or “image,” offers little value. An overly detailed description can interrupt the reading flow. The best wording explains the image’s purpose. It stays brief enough to remain useful.

When Alt Text Matters Most?

Alt Text needs special attention on pages containing product photography, diagrams, charts, maps, instructional screenshots, logos, and linked images. It’s also important when an image carries information missing from nearby copy. For a local organisation, a location image may need a meaningful description. This applies when the location supports the page’s purpose.

Review matters during website migrations and content updates. It also matters during template changes and large image uploads. Teams should check whether new templates preserve the alt attribute. They should check whether content editors understand meaningful imagery. They should also understand decorative imagery. WCAG provides the accessibility framework. Local legal duties may depend on the organisation, service, audience, and Australian requirements.