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Image SEO: Optimizing images for search engines

Whether you’re a blogger or you write articles for an online magazine or newspaper, chances are you’ll find yourself asking whether your article needs an image or not. The answer is always “Yes”. Images bring an article to life and can also contribute to your website’s SEO. This post explains how to fully optimize an image for SEO and provides some pointers on using images for the best user experience.

Always use images

Images, when used with care, will help readers better understand your article. The old saying “A picture is worth a thousand words” probably doesn’t apply to Google, but it’s certainly true when you need to spice up 1,000 dull words, illustrate what you mean in a chart or data flow diagram, or just make your social media posts more enticing.

It’s a simple recommendation: you should add images to every article you write online to make them more appealing.

Finding the right image

It’s always better to use original images – those you have taken yourself – than stock photos. Your team page needs pictures of your actual team, not this dude on the right or one of his stock photo friends. Off topic: never mind that dude needs a haircut.

Your article needs an image relevant to its subject. If you’re choosing a random photo just to get a green bullet in our SEO plugin’s content analysis, then you’re doing it wrong. The image should reflect the topic of the post or have illustrative purposes within the article of course.

There is a simple image SEO reason for this: an image with related text ranks better for the keyword it is optimized for. There’s more about image SEO later.

Alternatives

If you don’t have any images of your own that you can use, there are other ways to find unique images and still avoid stock photos. Flickr.com is a nice image source for instance, as explained in this article: How to Use Creative Commons Images from Flickr. I also like the images provided by sites like freeimages.com (formerly known as sxc.hu). Check here for more image resources. Steer clear of the obvious stock photos, picking the ones that look (ok, just a bit) more genuine. But whatever you use, It seems like images with people in them always look like stock photos, unless you took them yourself. In the end, that’s always the best idea.

Obvious alternatives for photos could be illustrations, which is what we use, or graphs. An honorable mention should go to animated GIFs, as these seem to be getting more and more popular these days.

But even though animated GIFs are popular, don’t go overboard. It’ll make your post harder to read, as the movement of the image distracts your readers’ attention. Like, for example, in the post where I found the image above.

Preparing images for use in your article

Once you have found the right image – whether an illustration, chart or photo – the next step is to optimize it for use on your website. There are a number of things you need to think about:

Choose the right file name

Image SEO starts with the file name. You want Google to know what the image is about without even looking at it, so use your keyword in the image file name. It’s simple: if your image is a sunrise in Paris over Notre Dame Cathedral, the file name shouldn’t be DSC4536.jpg, but notre-dame-paris-sunrise.jpg. The main keyword would be Notre Dame, as that is the main subject of the photo, which is why it’s at the beginning of the file name.

Scale for image SEO

Loading times are important for UX and SEO. The faster the site, the easier it is to visit and index a page. Images can have a big impact on loading times, especially when you upload a huge image then display it really small – for example a 2500×1500 pixels image displayed at 250×150 pixels size – as the entire image still has to be loaded. So resize the image to how you want it displayed. WordPress helps by automatically providing the image in multiple sizes after upload. Unfortunately, that doesn’t mean the file size is optimized as well, that’s just the image display size.

Use responsive images

This one is essential for SEO as well, and if you’re using WordPress it’s done for you since it was added by default from version 4.4. Images should have the srcset attribute, which makes it possible to serve a different image per screen width – especially useful for mobile devices.

Reduce file size

The next step in image SEO should be to make sure that scaled image is compressed so it is served in the smallest file size possible.

Of course, you could just export the image and experiment with quality percentages, but I prefer to use 100% quality images, especially given the popularity of retina and similar screens.

Optimize image file size using JPEGMini

You can still reduce the file size of these images by removing the EXIF data, for example. We recommend using tools like ImageOptim or websites like JPEGMiniPunyPNG or Kraken.io.

When you’ve optimized your images, test them with tools like YSlow.

Adding the image to your article

Now your image is ready to use, don’t just throw it into your article anywhere. As mentioned earlier, adding it close to related textual content helps a lot. It makes sure the text is as relevant to the image as the image is to the text.

Captions

The image caption is the text that accompanies the image on the page – if you look at the images in this article, it’s the text in the gray box below each one. Why are captions important for image SEO? Because people use them when scanning an article. People tend to scan headings, images and captions as they scan a web page. Back in 1997, Nielsen wrote: “Elements that enhance scanning include headings, large type, bold text, highlighted text, bulleted lists, graphics, captions, topic sentences, and tables of contents.” In 2012, KissMetrics went even further, stating that “Captions under images are read on average 300% more than the body copy itself, so not using them, or not using them correctly, means missing out on an opportunity to engage a huge number of potential readers.”

Do you need to add captions to every image? No, because sometimes images serve other purposes. Decide whether you want to use yours for SEO as well or not. Bearing in mind the need to avoid over-optimization, I’d say you should only add captions where it would make sense to the visitor for one to be there. Think about the visitor first, and don’t add a caption just for image SEO.

Alt text and title text

The alt text (or alt tag) is added to an image so there will be descriptive text in place if the image can’t be displayed to the visitor for any reason. I can’t put it any better than Wikipedia: “In situations where the image is not available to the reader, perhaps because they have turned off images in their web browser or are using a screen reader due to a visual impairment, the alternative text ensures that no information or functionality is lost.” Be sure to add alt text to every image you use, and make sure the alt text includes the SEO keyword for that page (if appropriate) and relates to and/or describes the image.

When hovering over an image, IE shows the alt text as a ‘tooltip’. Chrome shows the title text as was intended. Title text for images is similar and a lot of people who use titles simply copy the alt text, but more and more people leave them out altogether. What is it for? “The title attribute can be very useful, but it is not a safe way of providing crucial information. Instead, it offers a good way to provide non-essential information, for example, the mood of the image, or what it means in context.” – in other words, it’s ‘nice to have’ information, but isn’t taken into account for image SEO.

Read more: Read more about alt tag and title tag optimization »

OpenGraph and Twitter Cards

Earlier on, I mentioned using images for social sharing. If you add the following image tag to the <head> section in your page HTML like this:

<meta property="og:image" content="http://example.com/link-to-image.jpg" />

That will make sure the image is included in your share on Facebook (and OpenGraph is also used for Pinterest, for instance).

Our Yoast SEO plugin has a Social section where you can set and even – in the Premium version – preview your Facebook post. Make sure you use a high-quality image, like the original image you used in the post, as the social platforms use higher quality/larger images more often than not. If you have set this up correctly, and it doesn’t work, try to flush Facebook’s cache in the URL Debugger.

Twitter Cards do the same for Twitter and are also generated by our plugin.

Alignment

This is one of my pet peeves: Images should never break the left reading line. I’m sure there are studies backing this up, but for me it’s personal. I just really don’t like it when text starts to the right of an image, only to jump to the left the next image down:

Maintain the left reading line; don’t align images to the left

If you use an image at the same width as your text column, that’s fine and it will even help emphasize the image more.

I’ll be honest: this has absolutely nothing to do with image SEO, but I saw the chance to express my opinion and used it! I think it’s bad for user experience. So, just to please me: don’t do this. Thanks, I appreciate it.

XML image sitemaps

If you are a web developer, you might wonder about XML image sitemaps. I’d prefer to describe this as images in XML sitemaps. Google is pretty clear about this:

To give Google information about images on your site, you’ll need to add image-specific tags to a sitemap. You can use a separate sitemap to list images, or you can add image information to an existing sitemap. Use the method that works for you!

Every now and then, people ask us about XML image sitemaps. We don’t generate these in our plugin, but follow Google’s advice and include them in the page or post sitemaps. Just scroll down in our post sitemap and you’ll see we have added images to all our latest posts (there is a column just for that). Adding images to your XML sitemaps helps Google index your images, so be sure to do so for better image SEO.

Image SEO: summary

Image SEO is the sum of a number of elements. With Google getting better at recognizing elements in images every day, it makes sense to make sure the image and all its elements contribute to a good user experience as well as SEO. It would be foolish to try to kid Google.

Keep these things in mind when adding an image to an article:

Besides contributing to SEO and user experience, images can also play an important role in conversion!

Keep reading: Visually direct and captivate your visitors »