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Alt text

Alt text describes an image in simple terms—for people who cannot see it, but also for search engines.

What is alt text?

Alt text is an image description on websites that conveys the relevant information or function of an image. You usually don’t see the alt text unless the image fails to load. The short text in the source code is read aloud by screen readers when people with visual impairments use the page.

Search engines also read the alt text to better understand the image’s content and categorize it in image search results.

Good alt text describes concisely and as directly as possible what the image shows and, if necessary, what function it serves on the page.

Where did alt text originate?

Alt text has been part of the HTML standard since the 1990s. It is intended to provide a textual alternative when images cannot be displayed or perceived.

Over the years, it has become a central component of accessibility. As of June 28, 2025, the Accessibility Enhancement Act requires certain companies and digital services to comply with legal accessibility requirements. Alt text can be an important part of this.

Why is alt text important?

Alt text serves two functions:

It makes content accessible to people with visual impairments—a fundamental requirement that promotes inclusion and enhances legal certainty.

In addition, it gives images and the website additional opportunities for visibility in image search results, which in turn can serve as a source of traffic.

Advantages

  • Few measures offer so much benefit for so little effort.
  • Accessibility, image search, and contextual relevance are all addressed with a single field.
  • Alt text can also be implemented immediately—without any redesign or additional budget.

Challenges

The biggest hurdle is that every image that conveys content needs a description, no matter how small, and regardless of whether it’s the hundredth product photo.

In terms of content, the description must be accurate and not crammed with search terms, as this can be interpreted as manipulation.

In addition, you must distinguish between images that convey content and purely decorative elements. The latter are intentionally given an empty alt text so that screen readers skip them.

Example

A manufacturer of fastening technology maintains product images. Instead of the file name “product-123.jpg” without any further description, each image is given alt text such as “Stainless steel clamping lever M8 with red plastic handle.”

This allows search engines to better understand the images and index them for image search. Shoppers who are visually searching for a suitable product can land directly on the product page through these images.

Related terms

SEO (Search Engine Optimization) Search Engine Optimization, or SEO for short, is the process of optimizing a website so that it can be found by search engines like Google—ideally at the very top of the search results. Structured Data Structured data is additional information in the source code that helps search engines and other systems categorize a page’s content more accurately. UX (User Experience) User Experience (UX) is the experience a visitor has on a website or app. PageSpeed PageSpeed refers to a website’s loading speed—that is, the time it takes for the site to fully load and become usable. It is an important factor in user satisfaction and can affect search engine rankings.