Content Marketing Glossary

  • What is Alt Tag (Alt Text)?

What is Alt Tag (Alt Text)?

Alt Tag (Alt Text)

Alt Tag (Alt Text) is the written description of an image used by screen readers, displayed when an image fails to load, and read by search engines to understand what the image shows. Same thing, two names. Technically the attribute is `alt` on an `<img>` tag - most people call the description itself “alt text.”

If you write content for the web, this is the deliverable you’ll be asked about more than any other in an accessibility review - the most-cited, the most-skipped, and a quiet ranking factor that surprises teams when they finally do it properly.

What good alt text actually does

Write one sentence describing what’s in the image and why it matters in the context of the surrounding content. That’s the whole job.

For a photo of a chef plating a dish in a recipe post: “Chef plating roasted carrots with sumac yoghurt - the technique step described in the recipe above.”

For a screenshot of a dashboard in a how-to: “The Settings > Integrations panel showing the Slack connector enabled with channel routing configured.”

For a decorative graphic with no informational content: alt="" - empty alt, which tells screen readers to skip it entirely. Don’t write “decorative image of a wave.”

The three things to never do

Don’t write “image of.” Screen readers already announce that it’s an image. “Image of a chef” reads aloud as “Image image of a chef.” Just describe what’s there.

Don’t keyword stuff. “Best running shoes for marathon training cheap running shoes Nike Adidas running shoes review” isn’t alt text, it’s a 2008 SEO move that hasn’t worked since 2012. Google sees it, accessibility tools fail it, real users get nothing useful from it.

Don’t leave it blank when the image carries information. A blank alt on a chart that’s the entire point of the post means screen-reader users get nothing where sighted users get the data. That’s the failure mode WCAG audits flag every time.

An example of how much it actually moves

I worked with an e-commerce site selling outdoor gear that had 4,200 product images, most with auto-generated alt text from the product database - “Patagonia jacket black L” style. Functional but not great.

They ran one round of rewrites on their top-200 product pages: descriptive alt text noting colour, key features visible in the photo, and use case (“Black Patagonia Nano Puff jacket worn over a flannel, photographed in autumn light - showing the slim fit through the waist”).

Six months later: image search traffic to those 200 product pages up 47%, organic traffic to the same pages up 12% (Google appears to use alt text as a relevance signal beyond just image search). Same images. Same products. Twenty hours of writing time.

Where alt text and SEO actually meet

Image search is a real source of traffic in any visually-led category - recipes, fashion, travel, product reviews. Alt text is one of the main signals Google uses to understand what the image is, alongside the surrounding text and the file name. Treating it as both an accessibility deliverable and an SEO input is the realistic frame: write for the human listener first, and Google gets what it needs as a side-effect.

We built Penfriend to produce content with accessibility in mind, including sensible alt text suggestions for any imagery the content references. Alt text is a small craft signal that reveals whether a team is thinking about accessibility or not; getting it right at generation time avoids retrofit later.

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