Can AI be used to write good descriptive alt text for images in 2024?

The Importance of Alt Text for Accessibility and SEO

Alt text on images is an absolute basic of digital accessibility. Alt text (sometimes referred to as alt tags) is the alternative text, or text description, of an image providing some context of the image to users who cannot see it. This may include blind or low vision users, situations where the image doesn’t load or is broken, and also includes search engine crawlers. Alt text serves as descriptive text to convey the meaning and context of visual content in a digital setting.

Here in the UK, approximately 4.8% of UK adults have a vision disability that often requires the use of assistive technology for accessing the web.

Understanding image content poses a critical challenge for individuals with visual impairments, which should always be your first consideration, but providing good quality alt text - and indeed providing a highly accessible website - boosts your SEO efforts and will improve the experience for all of your users (not to mention making sure you're complient to ADA or the incoming EAA).

Alt Text Provides Context for Humans

So providing alt text is a win-win for everyone, but writing good quality alt text is still hard, and so many websites still often have poorly written alt text or fail to use it entirely, leaving an entire keyboard and assistive technology user group frustrated or left out. According to WebAIM, assistive technology users can expect a third of the images on popular home pages to have missing, questionable, or repetitive alternative text.

This is a shocking statistic to have in 2024, so, with the rise of AI and Natural Language Models, can we now offload the role of writing alt text to a bot?

TLDR - No. While AI can provide some basic context and provide a good start to generating alt text, a human is still needed to ‘sense-check’ the image and provide more context to the alt text that AI isn’t able to.

Qualities of Good Alt Text

Good alt text should be specific, concise, and relevant to the content and context of the image. It should avoid redundancy by not repeating information already provided by surrounding text. Additionally, it should capture the essential details without being overly descriptive.

In short: to write good alt text, think about how you would describe that image to a friend.

Testing AI Generated Alt Text Generators

We tested multiple different AI alt text generators for existing images, and settled on the following three for our tests: AltText.ai, Ahrefs Free AI Image Alt Text Generator, and Protoolio.

Note: Some of these AI alt text generator sites offered commission and affiliate links, but we aren’t using any affiliate links for transparency.

Criteria for choosing the tools

There are quite a lot of tools which claim to generate quality alt text using AI, but we wanted to narrow down our selection. The tools we chose matched the following criteria:

• It needs to be generally available to everyone. There exist some Shopify and Wordpress-specific tools which we didn't test.
• It needs a free tier, and we didn’t want to create an account.

The images we tested

We chose 3 images to test the AI alt text generators. The images were selected to cover a range of scenarios and complexities to see how well the AI alt text generators could handle them. The images were:

• A photograph of a beach sunset from Pixabay (we thought the AI would find this one easy)
• A photograph of Taylor Swift at the 2023 MTV Video Music Awards from Wikipedia
• An infographic from Moz explaining the importance of alt text

The beach sunset photo from Pixabay

AI generated results:

• AltText.ai: A heart shape drawn in the sand on a beach at sunset, with gentle waves in the foreground and a colorful sky with clouds.
• Ahrefs: A heart drawn on sandy beach at sunset.
• Protoolio: Serene beach at sunset with a heart drawn in the sand. Orange and pink hues illuminate the sky, reflecting on gentle ocean waves. Romantic and peaceful seaside scene.

Taylor Swift photo

AI generated results

• AltText.ai: Person with blonde hair and bangs wearing a black dress and multiple layered necklaces, standing against a colorful and dark background.
• Ahrefs: Taylor Swift's 'reputation' album cover with a snake, symbolizing negativity and controversy.
• Protoolio: Blonde woman wearing a black dress and layered necklaces at a red carpet event with colorful backdrop.

Infographic from Moz

AI generated results

• AltText.ai: Infographic titled “How does alt text provide context for humans?” explaining benefits: aids low/vision-impaired users, facilitates screen readers, and offers context for image load issues.
• Ahrefs: Alt text: “Image showing various examples of alt text, demonstrating how it provides context for humans.”
• Protoolio: Informative graphic by Moz explaining the importance of alt text in providing context for humans, particularly for individuals with low or impaired vision, users of screen readers, and addressing image load issues.

Conclusion

We were actually surprised with how well some of the results came out. Clearly, AI has come a long way, and Generative Language Models are able to create fairly accurate and useful alt text. However, the nuances and specific contexts still require human oversight to ensure the alt text is truly beneficial for all users, especially those relying on assistive technologies.