Content creators know the value images can bring to a webpage. Whether you lean on visuals to explain complex concepts, capture a visitor’s attention, or break up big blocks of text on the page, images can bring a blog post to life.
But did you know that they’re equally important for SEO?
I just checked the Moz cast for recent statistics on images in search, and at the time this article was published, almost 20% of Google Search results featured images.
Given that Google’s vision for the future includes a move towards visual search, an increasing number of people will be using images to discover information on the web.
All this means that if you’re not optimizing your images for SEO by using alt text, you’re missing out on a valuable source of organic traffic. While that leaves you at a competitive disadvantage now, it could result in more serious consequences for the future of your search visibility down the road.
Let’s take a deep dive into image alt text and then get down to some best practices and talk about how to optimize your images for search.
What is Alt Text?
Alt text is the copy that serves as an alternative to an image for those who cannot see it. You might see an image’s alt text if it fails to load on a page. For visually impaired visitors using screen readers, alt text provides context for the images in online content.
Likewise, because search engines cannot literally “see” visual information, the alt text attached to images provides important information about what the image contains and how it fits within the context of the rest of the page.
If you look at the source code of a web page, you’ll see alt text included in the HTML like this:
<img src=“image.jpg” alt=“image description”>
Why Is Alt Text Important?
From a functional perspective, alt tags improve accessibility for people who can’t see images on web pages. Accessibility matters to Google because it ensures a positive user experience for everyone.
From an SEO perspective, alt text is important because Google uses it with the contents on a page to understand what the image is about. If you use an image as a link, the alt text will function as anchor text, an important factor in search rankings.
Alt Text & SEO
Now that I’ve covered why alt text is important for both people and search engines let’s dive into more detail about how to use alt text as a larger part of your SEO image optimization strategy.
Google places a lot of value on alt text. Not only does it use an image’s alt text to determine what’s on the page, but also how it relates to the surrounding text.
In their article about Google image best practices, they go so far as to imply that adding image alt text can improve your conversion rates from organic traffic.
“By adding more context around images, results can become much more useful, which can lead to higher-quality traffic to your site.”Google Search Central – Content-Specific Guidelines
Image Alt Text Best Practices: 5 Things to Remember
When adding alt text, focus on writing useful, informative content that uses keywords appropriately and fits the content of the page. While it’s okay to write search-optimized alt tags, don’t forget that they’re first and foremost meant to be helpful to visually impaired users.
Here are some guidelines to help you craft SEO-optimized alt text for images that are equally helpful to users and search engines.
1. Be Specific
My best advice about writing image alt text is to imagine how you’d briefly describe it to someone over the phone. A few words might suffice, or you might need a full sentence. Most screen readers cut off alt text at about 125 characters, so anything longer won’t be helpful to the user.
2. Avoid Starting an Alt Tag With an Introduction
Since you’re working within a specific character limit, you don’t want to waste precious space (and user time) and introduce each image by identifying it as such.
For example, it’s not necessary to start your alt tag with phrases like these:
- This is a picture of a
- This picture shows
- Here’s a screenshot of
3. Incorporate Keywords But Avoid Keyword Stuffing
Use a keyword in your alt text if it’s relevant. Stuffing keywords into your alt tags creates a negative user experience. For instance, if my page has a pie chart that shows the most common types of featured snippets on a blog post optimized for “how to get featured snippets.” I could write an alt tag that says, “Pie chart of common featured snippets types.”
But “Pie chart of common featured snippets types to help you know how to get featured snippets” would be seen as keyword stuffing.
4. Don’t Repeat Content
Since the purpose of alt text is to provide digital copy about visual information, you don’t need to repeat existing content within an alt tag.
For example, if you have an infographic that illustrates the steps to changing a tire and the content of your post lists those steps and explains them, there’s no need to repeat the same information in your alt tag.
If there’s text in your image, should you include it in the alt tag?
It depends. Since neither Google or a screen reader can decode the text in an image, whether you include it in your alt tag will depend on how important that text is to the information on the page.
Some examples might include:
- the title of a book cover.
- the heading on an infographic.
- relevant brand names
4. Don’t Use Alt Descriptions for Decorative Graphics
According to Web Content Accessibility Guidelines (WCAG), an image is “decorative” if it has no function beyond the way it looks.
Don’t include alt text if an image is purely decorative, like a graphic divider or a background image. Because the image provides no valuable information, including its description in the alt text would “clutter” the screen reading experience.
Examples of Good & Bad Alt Text
Remember, your alt text doesn’t have to be long. Just make it as detailed and descriptive as it needs to be to benefit users. Based on the alt text best practices I outlined above, here are some good and not-so-good examples of alt text for images.
Bad: This is a picture of a girl.
Good: Young girl sitting on a bed at home using a digital tablet.
Good: Professional tailor using a measuring tape while altering a jacket in his workshop.
Bad: Pie chart.
Good: Pie chart of common featured snippets. 70 percent paragraphs, 19.1 percent lists, 6.3 percent tables, and 4.6 percent videos.
With graphs and charts, always include a link to the data source in the body copy. If you only add a citation to the image, visually impaired users can’t access more data.
Charts and graphs might sometimes call for a long description.
While writing great alt text is important, it’s only one part of a larger SEO image optimization strategy. Let’s dive into some of the other ways you can make sure the images in your content are helping and not hurting your overall SEO performance.
5 Ways to Boost Your SEO Image Optimization
1. Use Keywords in Image Names
It matters what you name your image files! When it comes to how to name images for SEO, you want to follow some of the same logic you follow for alt tags. The names of your image files should be relevant, descriptive, and include a keyword.
When naming images for SEO, include your keyword at the beginning of your image file name and separate words by hyphens (-). For example, for the pie chart example I included above, some possible file names might be:
This filename isn’t descriptive enough and doesn’t contain a keyword.
This filename leads with a keyword and is descriptive. Google can differentiate the words in the file name because hyphens separate them.
2. Use the “Right” Format
There’s no universally correct format for the images you use on your website. Which format you choose depends on the kind of image and how you want to use it.
Here are some guidelines:
- JPEGs are best for larger images to maintain clarity. In this case, “larger” means by dimension, not file size, which is a different consideration I’ll discuss below.
- PNGs will allow you to preserve background transparency.
- Scalable Vector Graphics (SVG) is a relatively new image format introduced in 2001 that remains crisp and clear at any resolution or dimension. SVGs can be animated, and like, PNGs preserve background transparency.
3. Right-Size Your Images
First off, I want to clarify the difference between image size and file size. The size of an image refers to its dimensions — for example, 1024 x 680 pixels. The size of a file refers to the amount of space needed to store it on a server — for example, 5000 kilobytes. The first relates to how much space an image takes up on a page, and the second relates to how long it might take to load.
Images with a high resolution and large dimensions contain a lot of visual information, which means they have a large file size and can slow your page load times.
Page load time relates to user experience and Google’s Core Web Vitals, which can impact your page ranking.
Be sure to resize your images before you upload them. Scaling the image with the display size option in a CMS (like WordPress) won’t improve page load time because the full-size image still needs to load before the display size is rendered on the page.
4. Use Captions
Theoretically, image captions could impact SEO if they contain keywords, but I’d advise against optimizing them specifically for organic search. While using a keyword in the file name and alt text of an image directly impacts its findability in search, image captions don’t serve the same function. Adding keywords to image captions could result in over-optimization and hurt your rankings more than they help.
Instead, view image captions through the lens of creating a positive user experience. Like headers, bulleted lists, highlighted text, and bolding, image captions enhance scanning on a page. We all know that folks tend to skim the content they read online, so offering signposts along the way helps them absorb the information you’re sharing.
Legend has it that advertising icon David Ogilvy commissioned research about including images in copy. One of the truisms* he shared that still resonates with marketers today is:
Captions under images are read 3x more than body copy.
If you’re not using captions with your images, you could be missing out on an opportunity to engage readers.
*I call this a “truism” because I couldn’t trace a path back to the original data source, so I can’t quote it as fact.
5. Add Alt Text
Adding alt text to your images is important to accessibility and SEO. Not convinced? You might want to review “Why Is Alt Text Important.”
What About Image Title Tags?
An image title is one more attribute that can provide information about an image.
The title attribute of an image can generate a tooltip for sighted users, but screen readers will skip over that text. As such, don’t isolate important information in image titles. Visually impaired visitors will not have access to it and it’s not a search ranking factor.
Free Tools for SEO Image Optimization
Here are some free tools to get you started with optimizing your images for SEO.
Image Optimization Tools
A quick Google search will reveal a whole host of free image optimization tools. Here are a few of my favorites:
- JPEG Optimizer
- Affinity Photo
- Kraken (bulk compression)
WordPress Plug-ins for Image Optimization
Load Speed Testing
There’s only one tool that I recommend to test the load speed of your pages after you’ve optimized your images. Google PageSpeed Insights will analyze load speed for mobile and desktop devices, give you a performance score, and identify opportunities for improvement. (Don’t know why page speed matters? Read up on Google Ranking Factors and uncover the most important things for getting to the top of the search results.)
Get Help With SEO Image Optimization
Using alt text and optimizing your images for search represents an SEO opportunity that many of your competitors are missing out on. While there are a lot of variables to consider when you set out to leverage the power of image search, you don’t have to go it alone. When you schedule a free SEO consultation, ask about image optimization opportunities for your website.