Alt Tags in SEO

19th January 2019

Alt Tags in SEO

The term “alt tag” is a commonly used abbreviation of what is actually an alt attribute on an img tag. The alt tag of any image on your site should describe what is on it. Screen readers for the blind and visually impaired will read out this text and therefore make your image accessible.

What are alt tags and title tags?
This is a complete HTML image tag: <img title=”“image” src=”“image.jpg”” alt=”“image” />

The alt and title attributes of an image are commonly referred to as alt tag or alt text and title tag – even though they’re not technically tags. The alt text describes what is on the image and the function of the image on the page. So if you are using an image as a button to buy product Y, the alt text should say: “button to buy product Y.”

Visually impaired person with guide dog feeling link with white stickThe alt tag is used by screen readers, which are browsers used by blind and visually impaired people, to tell them what is on the image. The title attribute is shown as a tooltip when you hover over the element, so in the case of an image button, the image title could contain an extra call-to-action, like “Buy product Y now for £29!”.

Each image should have an alt text, not just for SEO purposes but also because blind and visually impaired people won’t otherwise know what the image is about, but a title attribute is not required. What’s more, most of the time it doesn’t make sense to add it. They are only available to mouse (or other pointing devices) users and the only one case where the title attribute is required for accessibility is on <iframe> and <frame> tags.

If the information conveyed by the title attribute is relevant, consider making it available somewhere else, in plain text and if it’s not relevant, consider removing the title attribute entirely.

But what if an image doesn’t have a purpose?

If you have images in your design that are purely there for design reasons, you’re doing it wrong, as those images should be in your CSS and not in your HTML. If you really can’t change these images, give them an empty alt attribute, like so:

<img src="image.png" alt="">

The empty alt attribute makes sure that screen readers skip over the image.

alt text and SEO

Google’s article about images has a heading “Use descriptive alt text”. This is no coincidence because Google places a relatively high value on alt text to determine not only what is on the image but also how it relates to the surrounding text. This is why, in our Yoast SEO content analysis, we have a feature that specifically checks that you have at least one image with an alt tag that contains your focus keyphrase.

We’re definitely not saying you should spam your focus keyphrase into every alt tag. You need good, high quality, related images for your posts, where it makes sense to have the focus keyword in the alt text. Here’s Google’s advice on choosing a good alt text:

When choosing alt text, focus on creating useful, information-rich content that uses keywords appropriately and is in context of the content of the page. Avoid filling alt attributes with keywords (keyword stuffing) as it results in a negative user experience and may cause your site to be seen as spam.

If your image is of a specific product, include both the full product name and the product ID in the alt tag so that it can be more easily found. In general: if a keyphrase could be useful for finding something that is on the image, include it in the alt tag if you can. Also, don’t forget to change the image file name to be something actually describing what’s on it.

alt and title attributes in WordPress

When you upload an image to WordPress, you can set a title and an alt attribute. By default, it uses the image filename in the title attribute, which, if you don’t enter an alt attribute, it copies to the alt attribute. While this is better than writing nothing, it’s pretty poor practice. You really need to take the time to craft a proper alt text for every image you add to a post — users and search engines will thank you for it.

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