Google’s Advice on Writing Alt Text for the Best SEO Outcomes

As Google’s Search Advocate, John Mueller has long been a font of knowledge for those in SEO. More than any other public-facing figure, he consistently drops insights into how Google’s algorithms truly work, suggesting best practices in plain English. In September 2024, Mueller took a question from Reddit about writing alt text properly.

Photo by Max Chen on Unsplash

On-Page Assets & Alt Text

Online, most well-made sites load assets embedded into the webpage. Most commonly, these are images attached to articles and other media like reviews or tutorials. Algorithms can’t tell what these images show, so alt text describes them. It only takes one or two sentences, with no frills. They also display for readers if the image cannot load, for some reason.

Images are just one kind of on-page asset out there. For example, an online video player is an on-page asset if a YouTube video is embedded into your page. Alt text exists for video too, giving the algorithm valuable context. There are also interactive assets on certain websites, best seen in the iGaming industry today. These are sites that offer digital games filled with unique digital art, from slots to other classics like Plinko gambling games. In those cases, the interactive window is another on-page asset, and alt text can once again help algorithms figure out that it’s looking at a game.

Behind the scenes, alt text is framed as an HTML attribute. These HTML elements make up every page that you visit online, including the one you’re reading now. Adding alt text gives depth to these attributes, which gives the algorithms a better idea of what your page is about.

John Mueller’s Alt Text Advice

Now that we have some idea of what alt text is, let’s go to John Mueller’s response to a user’s question about image alt text, specifically. That user asked: “Are images alt texts still relevant for SEO with all the computer vision and images recognition advancement?”

This user is highlighting that Google’s progress with machine learning has come a long way. In 2024, Google searches now come fully equipped with Gemini AI summaries that can answer direct questions and gather supporting evidence in seconds, all while understanding context. This includes the ability to ‘look’ at images and even make them.

John Mueller’s response could be summarised in three words – context is key. While using computer vision could help algorithms 'see' a photograph published online, the alt text adds valuable context. In his response, Mueller writes: “A photo of a beach might be a relaxing poster, it might be the beach from a hotel, it could be the site of a chemical spill,” to highlight just how impactful context can be.

Source: Unsplash

The alt text is a bridge between the image and the page, making it unique among HTML attributes. Mueller goes on to highlight why using AI may cause more confusion. He says using AI to write alt text is how you get vague, out-of-context results like that beach photo example. At present, you can provide a better description than any known AI model.

This may change in the future, as Google is always looking to update its tools. AI will continue to improve and one day, may be able to find deeper context in images once combined with copy from the page itself. However, SEOs should stick to writing their own alt text for the foreseeable future.