Why alt texts are important for SEO and accessibility

Images make your website more visually appealing. They attract attention, clarify your message and increase visitor engagement. But did you know that images also contribute to your findability in search engines, provided you use them correctly? A crucial part of this is the use of alt text. In this extensive article we explain what an alt tag is, why it is important for SEO and accessibility, and how to apply it correctly with practical HTML examples.

What is an alt tag?

An alt tag, or more accurately an alt attribute, is a piece of text that you add to an image in the HTML code. It stands for "alternative text" and is used to describe what can be seen in the image.

Example of an HTML img tag with alt text:

<img src="taart.jpg" alt="Vressgebakken appeltaart met slagroom" />

This text is displayed if the image cannot be loaded and is also read by screen readers for people with a visual impairment.

Why are alt texts important for SEO?

Alt texts play an important role in search engine optimization (SEO). Here are the main reasons:

• Search engines can’t “see” images. They rely on alt text to understand what’s in an image.
• Images can rank in Google Images. Good alt text increases the chance that your image will appear there.
• Alt text contributes to your overall page relevance. Especially if it supports the topic of your page.
• It improves the user experience. Not only for people with disabilities, but also if the image doesn’t load due to a slow connection.

Alt text and accessibility

Accessibility is an important part of modern websites. Screen readers use alt text to tell what’s in an image. Without alt text, people with visual impairments miss important information. This is not only good for your visitors, but also legally required for many organizations.

How do you write a good alt text?

A good alt text:

• Clearly describes what is on the image
• Is concise (usually 5 to 15 words)
• Contains relevant keywords (but not excessively)
• Is useful if the image is not shown

Example good:

<img src="fiets.jpg" alt="Blue ladies bike with basket on the beach" />

Example bad:

<img src="fiets.jpg" alt="Afbeelding" />
<img src="fiets.jpg" alt="" />

What if an image is purely decorative?

Then use an empty alt text: alt="". This ensures that screen readers skip the image. Only do this if the image has no substantive value.

Images and keywords

You can use relevant keywords in your alt text, but do this in a natural way. Avoid keyword stuffing. An example:

<img src="seo-checklist.png" alt="SEO checklist with tips for higher ranking" />

Alt text in combination with title attribute

Sometimes you also see the title attribute used, which shows text when you hover over the image with your mouse. For SEO it is less important than the alt text, but it can provide additional context:

<img src="team.jpg" alt="Our marketing team at work" title="Meet our team" />

Using alt text in CMS systems

In WordPress, Shopify or other content management systems you can usually enter alt text directly when uploading an image. Always fill this in — many people forget this and miss out on SEO opportunities.

Tips for large websites with many images

• Use a standard format or template for alt text for product images
• Regularly check for images without alt
• Use tools such as Screaming Frog or Ahrefs to detect missing alt attributes

Common mistakes with alt text

• Forgetting to fill in alt text
• Stuffing alt text with keywords
• Using alt text that is not descriptive (such as "photo" or "picture")
• Provide decorative images with meaningful alt text

Check your alt text

Use browser extensions or tools such as:

• WAVE Web Accessibility Tool
• SEOptimer

Summary

Alt texts are essential for a good SEO strategy and for the accessibility of your website. They help search engines and users with disabilities to understand what is in your images. By providing each image with a relevant and clear alt text, you improve the user experience and your position in the search results.

Checklist: what to do?

• Give each content image a descriptive alt text
• Use relevant keywords, but don't overdo it
• Leave the alt attribute empty for decorative images
• Regularly check for images without alt

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