What are alt tags?

Alt text, or alt tags, are used to describe images on a website and their function on the page. Alt tags aren’t something you see when you normally view a website. They’re primarily used by screen readers for people who are blind or visually impaired, and by search engine crawlers that help identify and categorize images. 

Because they play a role in your overall SEO strategy (and in ADA compliance), it’s important to understand when and how to use alt tags—and what makes a good alt tag in the first place.

When should you use an alt tag?

Always. Every image should have an alt text that properly describes what the image is about. But what if the image has no purpose and is only decorative? Or what if its already being described somewhere else, like in the web copy? Images like these should have what is known as an empty alt tag. An empty alt tag makes sure that screen readers skip over the image, improving the user experience.

This is an example of a decorative image:

Note that the alt attribute is still present, even though nothing is written between the quotation marks. When a screen reader comes across the empty alt text, it will skip over the image without announcing its presence. If no alt attribute is present, the screen reader will read the file name for the image instead, which can be a major distraction to those using screen readers. 

What makes a good alt tag?

Now that we know when to use them, the question is what makes a good alt tag? You might be tempted to flood your alt tags with keywords knowing that search engines are looking at these images. Google won't downgrade you for poorly written alt tags, but if you use your alt text as an instrument for keyword stuffing, that’s when you will get into trouble.

The better solution is to focus on writing descriptive alt tags that provide meaning to your images and include your target keyword only when it fits naturally. Most screen readers don’t go beyond 125 characters for alt text, so it's best to stick to that character count or less.

Good Alt Tag Examples

Here are a couple examples of well written alt tags in action:

While this alt tag is short, it perfectly describes this simple photo. Not all alt tags need to be long sentences. As long as you accurately describe the photo, you’re set.

Unlike the photo of the odd-eyed cat above, this image is a little more complex. To truly convey the contents of the Starry Night, you need to have a much longer and more detailed description.

Optimize Your Alt Tags at Any Time

So, now that you know the basics of alt tags, where do you start when developing alt tags for your current blog posts and webpages? Perform a basic audit of your existing content and see where you can incorporate alt tags into previously untagged images. Watch to see how your organic traffic changes among the pages that you give new alt tags.

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