Alt Text for Images: Accessibility Win, But What About SEO?

By Chris Evans. Posted 26/03/26 (updated: 1/04/26)

Alt text is often discussed from an accessibility perspective, but what about SEO? Can adding alt text to images actually improve organic search performance, or is it just a best practice with no real ranking impact? This is the question I set out to answer in my latest SEO experiment.

My Rationale

Whilst many other SEOs were obsessing over the latest Google updates, I took the time to focus on the observed human factors in SEO. I was watching how friends, family, and basically anyone performed their searches and how they interacted with the results they were presented with. One clear thing began to stand out: that most SEOs were ignoring image search altogether.

When you combine this with search data from tools like Ahrefs and SEMRush, which show that up to 25% of searches in some sectors are image-based, I had to test a theory to see if more organic traffic could be generated from image improvements.

Over the last 2 years, I have conducted several experiments, albeit on a small data set, to determine whether image ALT text has a significant impact beyond accessibility, specifically on SEO results. Of course, using AI tools to generate alt text now makes the process more affordable while maintaining the same impact.

What Makes a Good ALT Text?

Not all alt text is created equal. For this test, the goal wasn’t just to add alt text for the sake of it, but to add alt text that actually helps search engines understand the image and its relevance to the page.

Good alt text should be descriptive, relevant, and written for humans first. It should clearly describe what is in the image while also reflecting the page’s context. Where relevant, keywords can be included, but only if they fit naturally into the description. Keyword stuffing alt text is easy to spot and doesn’t help users or search engines.

As a general rule, the alt text used in this test followed a simple structure:

Describe what is in the image.
Include relevant product, service, or location information where appropriate.
Keep it natural and readable.
Keep it relatively short (usually under 125 characters)
Avoid keyword stuffing
Avoid generic alt text like “image”, “photo”, or file names.

Example of Poor ALT Text

“shoes”
“image1”
“red dress buy online cheap red dress free delivery”

Example of Better ALT Text

“Black running shoes with white sole on a wooden floor”
“Plumber repairing a kitchen sink in York”
“Woman stood in garden setting, wearing a blue summer dress with a floral pattern”

The key takeaway is that alt text should describe the image in a way that makes sense if the image can’t be seen, while also providing search engines with more context about the page. When done properly and at scale, this is where the SEO benefit appears to come from.

The Method Behind the Test

For this study, I focused on answering two main questions that drive most decisions about alt text:

Does adding alt text to images provide a measurable SEO benefit?
Does the potential gain justify the time and resources required to implement it consistently?

While alt text is often recommended for accessibility, I wanted to see whether it also moves the needle on organic performance and whether the return on investment makes it a worthwhile task for businesses across different industries.

Adding alt text to every image can be a huge time sink, especially on sites with hundreds or thousands of visuals. Doing it manually takes time and attention to get it right. Even on a small website, I found it took around 10–15 minutes per image from start to finish. While AI tools can speed up the process, the results aren’t always perfect.

Using AI tools like ChatGPT can make this much faster. You can generate alt text for dozens or even hundreds of descriptive images in minutes rather than hours, though the output often needs a quick review and tweak to ensure relevance and accuracy. It’s not a fully hands-off solution, but it strikes a practical balance between speed and quality, making the process far more manageable without losing SEO or accessibility value.

For this case study, I combined OpenAI with Screaming Frog to automate the initial alt text creation. The time and cost benefits were too compelling to ignore. Costs can vary depending on the complexity of the images, the number of outputs required, and your subscription plan, but in this test, I was able to create around 1,000 image alt texts for roughly £10-15 of API credits, then just a few hours of tweaking and uploading, depending on the number of images.

Setting Up The Test

To keep the test as controlled as possible, no other major SEO changes were made during the test period. The only variable changed was the addition of optimised alt text to existing images.

Alt text was added to all existing images on the site. Performance was measured using Google Search Console, comparing an 8-week period before the changes to an 8-week period after, or a year-on-year 3-month period from the data of change, where available. Metrics tracked included clicks, impressions, and traffic from image search.

Impact on SEO and Effort

The results of our test weren’t uniform. While adding alt text generally had a positive impact on SEO, the size of that impact varied depending on factors such as niche, sector, CMS, and even the types of images used on the site. Some industries saw noticeable uplifts in organic performance, while others experienced little to no change. This variation highlights that alt text isn’t a one-size-fits-all solution; it works differently depending on the context, but it still provides value both for accessibility and, in many cases, for search performance.

eCommerce ALT Texts

Of all the tests I ran, alt text had the biggest impact on e-commerce websites. One site in the ladies’ fashion sector saw a 230% increase in daily clicks from image search and a 33% increase in overall clicks (including image, web, and video traffic) during the 8-week test period compared to the 8 weeks prior.

On another e-commerce site, a broader marketplace, the results were positive but less dramatic. Organic search clicks increased by 48%, while impressions jumped 500%. This shows that while alt text can significantly boost performance in some e-commerce niches, the impact can vary depending on the site and its audience.

ALT Texts For Local SEO

Tracking the impact of alt text on local SEO proved trickier because Google Search Console reports data in a way that makes it difficult to pinpoint the search location. I couldn’t isolate clicks coming solely from the target geographic area. That said, the results were still positive, though not as dramatic as what we saw with e-commerce sites. Alt text appeared to contribute to incremental gains in organic visibility, but the effect was smaller and more nuanced in local SEO contexts.

For a site targeting customers in North Yorkshire, I ran a year-on-year comparison after creating localised, factual, and relevant alt text using AI. When filtered in Google Search Console, the data showed a 700% increase in clicks and a 650% increase in impressions from image search.

When I ran the same test on the Mayfly Internet Marketing website, the results were far less dramatic. Clicks increased by just 3 over the same period, although impressions rose by 534%. Much like the eCommerce tests, this reinforces the idea that the niche a website operates in plays a major role in the effectiveness of alt text optimisation.

ALT Texts For National SEO

I ran the same test on a website that serves two SEO purposes: promoting the franchise side of the business nationally and attracting local customers for individual franchise owners. Initial results suggested a negative impact on SEO, with overall clicks down by 30%. However, when I analysed the queries in more detail, the losses were coming from keywords the website was not actively targeting, while gains were seen in more relevant, higher-intent keywords. In other words, traffic decreased overall, but the traffic’s relevance improved.

ALT Text Case Study Key Takeaways

While the sample size is relatively small, the tests revealed some consistent trends. Alt text had the greatest impact on websites where images play a major role in how users search and browse, such as fashion and e-commerce. For local and service-based businesses, the impact was smaller but still positive in terms of visibility. Perhaps most interestingly, in some cases, overall traffic decreased, but rankings improved for more relevant keywords, suggesting that alt text may help search engines better understand image context and page relevance, not just drive more image search traffic.

Site Type	Click Change	Impression Change	Impact
Fashion eCommerce	+33%	+230%	High
Marketplace eCommerce	+48%	+500%	High
Local Business	+700%	+650%	Medium
B2B SEO	+3	+534%	Low
National Franchise	-30%	Relevance improved	Mixed

So, Is Adding Alt Text Worth It for SEO?

The classic SEO response of “it depends” feels very appropriate for this case study.

Whilst adding alt text is now far more cost-effective thanks to AI, it will always deliver accessibility improvements, which in itself is a strong enough reason to implement it. However, from a purely SEO perspective, the impact appears to depend heavily on the sector the website operates in, how important images are to the customer journey, and whether the website has the potential to generate traffic from image search.

Based on the tests in this case study, the takeaway is fairly clear:

100% yes for eCommerce websites, particularly in visually driven sectors like fashion, home, beauty, and anything where users are likely to search via images.
100% yes for image-heavy websites, where images are a core part of the content and user experience.
Maybe for local SEO, where the gains are smaller but still positive, particularly in image search visibility.
Less impact for B2B and service-based websites, where users are less reliant on image search and more focused on traditional web results.

What this suggests is that alt text optimisation is not a universal SEO win, but in the right niche, it can be a significant opportunity, particularly when implemented at scale with AI tools to reduce time and cost.

If nothing else, this case study shows that image search is still an underused channel in SEO, and alt text is one of the simplest ways to improve visibility there. For many websites, especially in e-commerce, this is likely an opportunity worth exploring.

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Chris Evans

Chris Evans is SEO Lead at Mayfly, where he leads organic strategy end to end across technical SEO, content planning and performance reporting. He joined in 2025 with over a decade of hands on experience optimising sites in e-commerce, local search and enterprise environments. Chris is comfortable getting into the code when needed, working with HTML, CSS and JavaScript to diagnose and fix issues that hold visibility back. He also uses advanced analytics and practical AI workflows to uncover opportunities and improve user experience.