What is Alt Text and How Does it Factor into SEO?

Search Engine Optimization (SEO) is a big topic. It’s made up of hundreds of techniques that can help your website rank higher in the organic search results.

At the highest level, SEO involves tweaking your website to make it easier for humans and search engines to understand. This involves improving content, navigation, links and site structure.

At the micro level, SEO includes tiny changes, like adding alt text to images.

Providing alt text for every image on your website is a big task. But it’s crucial to accessibility and your SEO efforts. To find out why, experts at Gordon Digital SEO are going to explore what alt text is, how it factors into SEO, and some tips on writing effective alt text for your website.

What is Alt Text?

Alt text is a HTML attribute that describes the subject matter of an image on your website. This text is used by search engines and screen readers to understand the content of an image.

Alt text is attached to the HTML code that’s used to display an image. It looks like this:

<img src=”border_collie.jpg” alt=”Border Collie”>

This alt text won’t be displayed on the page under normal circumstances. It can be read by search engines and screen readers, but will only appear on the page if the image fails to load:

Example of a broken image with alt tex.

You aren’t required to provide alt text for images. It’s good practice to write alt text for any images that are relevant to the content on the page. If you don’t want to provide alt text for a particular image, you can simply leave the attribute blank:

<img src=”border_collie.jpg” alt=””>

This improves the user experience for anyone that’s using a screen reader, but it won’t help your search rankings.

Alt Text vs Image Captions

Writing alt text is a little bit like writing a short caption for an image. But alt text and image captions are two distinct things in the world of SEO.

Alt text is used by search engines to help understand the subject matter of an image, but it won’t be displayed on the page.

Image captions can also help search engines understand an image. The caption will appear on the page, underneath the image:

You can include an image caption by adding the “figcaption” HTML code:

<img src=”border_collie.jpg” alt=”Border Collie”>

<figcaption>Caption goes here.</figcaption>

Image captions are generally longer and more descriptive than alt text. An image caption may include copyright, photo credits, location information and other details.

How Does Alt Text Factor into SEO?

Writing alt text for the images on your website supports your SEO strategy in a few different ways:

1. Help Google Understand Your Content

SEO optimizes your website so it appears higher in the organic search results.

The challenge is that search engines use AI-powered robots to discover your website. These robots don’t view web pages the same way humans do – they look at the HTML code powering the site. This creates a problem when it comes to images.

Images are displayed as a file path within HTML code. While Google knows that you’ve placed an image on a page, it can’t tell what the image contains. This is problematic for images that are relevant to the content on the page.

Adding alt text makes your content higher quality and more authoritative. This may give you a boost in the organic search rankings.

2. Meet Accessibility Guidelines

Adding alt text to images is a requirement set out by W3C’s Web Content Accessibility Guidelines.

The internet is used by everyone – including people with impaired vision. Making your website accessible means it’s more inclusive. It can also help generate conversions by making your content easier to navigate and understand.

Alt text is crucial to supporting people who use screen readers to turn visual content into auditory content that’s easier to absorb.

Like Google’s robots, screen readers use the HTML code, so they can’t tell what an image looks like without help. Screen readers will read out alt text to help the user understand the content on the page.

If you don’t provide alt text then a screen reader is likely to read out the image file name instead. These are often confusing or unrelated to the actual content of the image, which creates a poor user experience for visually impaired people.

3. Improve User Experience

Alt text doesn’t just help visually impaired people. It also improves the general User Experience (UX).

UX is a major ranking factor for Google. Google’s mission is to provide customers with the most relevant search results possible. If a user visits a search result and is greeted with a poor UX, they’re likely to leave the web page and try to find the answer somewhere else.

It’s important to consider UX when optimizing your website. This includes basic SEO tasks such as:

  • Providing easy-to-use navigation and menus
  • Structuring content to create a logical flow of ideas
  • Making the relevant information easy to understand
  • Writing quality content that answers the user’s search query
  • Ensuring content (including text and images) loads and displays as intended

This last one is important. Content that doesn’t load as intended won’t help the user, and Google considers this a poor experience.

One of the most common problems with websites is images that fail to load. When this happens, the alt text will be displayed instead. This means the user can still benefit from the image, even if they can’t see the image.

4. Generate Organic Traffic from Images

SEO focuses on getting your web pages to show up higher in the organic search results. But web pages aren’t the only thing that can rank – images can too!

All major search engines provide an image search function. Research from Moz has shown that searches associated with graphic results can generate up to 50% of their traffic through image search.

This is an enormous opportunity to attract organic traffic to your website.

Google’s robots rely on image captions and alt text to understand the subject matter of an image. Providing these details will help your images rank higher in organic image searches. Images that rank highly can also show up in the “image pack,” which may be displayed as part of Google’s normal search results, further increasing your website’s visibility.

Best Practices for Writing Image Alt Text

Adding alt text to your images can improve your organic search rankings and make your website more user-friendly. If you want to see the full benefit, you should follow these best practice tips:

1. Add Alt Text to Relevant Images

The goal when writing alt text should be to make your website easier to understand for users and search engines alike.

This means we need to write alt text for images that are relevant to the content on a given page. For instance, we recommend that you don’t write alt text for decorative images (such as header images). These images don’t necessarily relate to the content on the page. Writing alt text for these images can be confusing to search engines and visually impaired users.

Instead, decorative images should receive an empty alt attribute:

<img src=”header_image.jpg” alt=””>

You should write alt text for images that provide additional context or information to the reader. This includes things like:

  • Charts and other images that illustrate data (especially if the data isn’t mentioned in the body of the text)
  • Images that provide additional information (e.g. before and after photos)
  • Icons that are functional or used for navigation (e.g. arrow icons used to navigate between pages)
  • Images used to provide instructions on a process
  • Images that contain useful text (e.g. photos of a book, or screenshots of a social media post)

2. Include Your Keywords

Remember that alt text can help search engines understand the content on your website. That means alt text is a good place to include keywords for the web page.

Be careful not to stuff your keyword into every image on the page. This is bad SEO practice and can negatively affect your organic search rankings. However, if you can use a keyword naturally while writing alt text, it’s a good way to boost rankings.

Using keywords when writing alt text is useful if you want your images to display in Image Search results. This can increase traffic to your website and help more customers find your content.

3. Be Descriptive

Alt text should concisely describe the content of an image, and/or the image’s purpose on the page. This means the same image could have different alt text when used on different pages.

For example, the image below could have the alt text “Puppy learning to lie down” if it appeared on a page about dog training.

The same image could have the alt text “Border Collie puppy with black and white fur” if it appeared on a page about different dog breeds.

Effective alt text should be as descriptive as possible in just a few words. If we take the image above as an example, we could use any of the following alt text descriptions:

  • Good: Puppy
  • Better: Border Collie puppy
  • Best: Border Collie puppy lying in the grass

The alt text you choose would depend on how the image is used on the page, but each of the above examples is valid.

Your alt text doesn’t need to include any of the following:

  • Photo credits
  • Copyright ownership
  • Phrases like “image of”
  • Content that users need (this belongs in the image caption, or the body of the text)
  • Information that’s already included in the image caption or the body of the text

4. Use Alt Text Tools

SEO apps like Semrush make it easy to add alt text to the images on your website. If you use Semrush, the SEO Writing Assistant can take the work out of optimizing your website.

When writing alt text you should keep to a maximum of 125 characters. Many screen readers stop reading alt text at this point, so users may miss out on vital information.

W3C provides additional guidelines on how to write descriptions for complex images.

Tying it All Together

Optimizing alt text is a great way to increase organic search rankings and make your website easier to use.

This small detail is an important part of a strong SEO strategy. It also goes a long way to building a cost-effective marketing funnel!

We recommend starting with the most popular pages on your website. Identify the pages with the highest traffic and begin optimizing your alt text. After you’ve updated your existing images, make it a habit to write alt text for any new images that are uploaded to your site.

That way, your website will be accessible to everyone, and you’ll be on your way to kicking your SEO goals!


Interesting Related Article: “Understanding SEO Algorithms