Image optimization for SEO – The Ultimate Guide

Posted by Clif Haley on 24 Mar, 2020
View comments SEO
If you're not doing image SEO you're missing out. Here's a step-by-step guide to everything you need to know.

Image SEO.

ID 113811052 © Thodonal |

Whether you're a blogger, a contributor to an online publication, or you're in charge of posting relevant content to your company's website, you may often find yourself asking whether it's worth adding images to your post.

The answer is always, "Yes."

Not only do images play a vital role in breaking up large swathes of text to hold the attention of readers for longer (increasing time on page), but they also play an active and often underestimated role in the SEO of an article or blog post. In addition to providing eye pleasing content for website visitors, it also provides search engines access to images that can be indexed and served in image searches such as Google Images and Bing Images.

This guide will provide a list of easy pointers to follow regarding image optimization for SEO.

But before we delve into step-by-step practical advice, it's worth restating the case for the using images within online articles and blog posts.

Why using images is so important

When used correctly, images first and foremost help to engage readers so that they can better understand your article. While a picture doesn't "paint a thousand words" in the eyes of Google, they are great at breaking up texts that run into thousands of words.

In today's attention-starved world, a reader is more inclined to scan an article rather than digest a blog post, sentence-by-sentence. Therefore, a well-placed image coupled with a well-thought- out caption can help to retain the focus of your average website visitor (we'll get to this later).

When it comes to search engines, images are also taking on an increasingly important role. Just look at Google's investment into visual search, which is only set to accelerate with the proliferation of Google Lens. Today, 28% of SERPs feature images, which means if you're not using them effectively, you're being left behind by competitors who are.

How to find the right image?

Image optimization for SEO purposes begins with the very image itself. Careless webmasters frequently put too little thought into their image choices and into how such images are acquired.

While it may be tempting to simply visit Google Images and “save as” any image you like, this is not only ill-advised but potentially illegal. Most images are owned by someone – be it an individual or a company – and when you take an image directly from an image search (or from another website) you are in a sense stealing. To this end, let’s briefly go over...

Image usage rights

Image rights.

ID 173050036 © Melpomenem |

Royalty-Free images – Royalty-Free images are images offered by an individual or stock photography agency such as Dreamstime for sale. When you pay for the image you are paying for the right to use the image. The creator of the image is compensated for their creative work and you are legally allowed to use the image. This is of particular importance when using images prominently featuring recognizable people and models. People have some control over where and how their likeness is used. Legitimate royalty-free images featuring models will be backed by a “model release” in which the model has legally consented to their likeness being sold as a stock image for re-use.

Public domain / Creative Commons Zero – When a photographer has agreed to distribute their work for use under the Creative Commons Zero license as a public domain image, they are essentially allowing anyone to use their images in any way they see fit without having to pay for it or credit the photographer.

This is not necessarily an ironclad guarantee that you won’t face some future problems using these images, however. If they prominently feature people or an individual person, that person may still object to their likeness being used even if the photographer has “given away” the usage rights of the image. In the end, the safest bet for any webmaster wanting to use images on their site is to acquire them from a reliable stock photography agency like Dreamstime.

If you're trying to rank the image in its own right (e.g., an infographic), then the higher up the page, the better. But again, only if it fits within the context of the article. There's a reason for this emphasis on relevancy, images surrounded by highly relevant text rank better for the keyword it's been optimized for, but more on that later.

Choose the right file name

That's right, image optimization for SEO begins before you even hit "save" on the file in question! The right file name can make all the difference to your Google results. Remember, page crawlers aren't physically looking at the image.

We're all guilty of saving our own photos with catchy names such as image00023451.jpg, but that isn't going to help when the Googlebot shows up to index the images. If you're a travel blogger writing a post about the best surfing beaches in Bali, and you've found a great picture of you "nailing a tube" from your vacation there six months ago, or found a relevant stock photo online, “then best-surfing-beaches-bali.jpg” would be a much more apt name.

Remember to put your main keyword at the front of the image, as it immediately alerts Google to what your image pertains to.

Choosing the image format

When it comes to file format, there's no clear winner. It depends to a certain extent on the type of image, and how you're using it. Here's what you need to take into account:

· JPEG – better for larger photos, this format will give you good quality images without coming in at a massive file size.
· PNG – Best for those looking for high-resolution images (particularly if you want a transparent background), however, file sizes tend to come in a little larger than JPEG counterparts.
· GIF – Great for adding those memes, but more extended animated memes can take a toll on page load speed if not optimized correctly.
· SVG – Good for logos and icons. With the help of JavaScript, they can be resized without a loss in quality.

Getting the right image scale

As briefly mentioned above, page load speeds are critical when it comes to SEO. The faster a page loads, the quicker it is to visit and index. Large images will slow page loading times right down, even if the image is displayed in a small pixel format. For instance, a vast 2000 x 3000- pixel image viewed as 200 x 300 pixels still requires the loading of the original image.

Therefore, scaling the picture to manageable sizes is a good idea, to negate the effect it has on page load speed. WordPress does offer preset sizes, but you may have to take on your own scaling measures to get the image precisely as you'd like it. But remember, this is the process of rescaling the picture, not the resizing of its source file. That comes next.

If you know the exact size your image will render on a site regardless of device (e.g. if the “slot” for the image on the site is always going to be 250 pixels x 250 pixels) then you can crop your image to that exact size. This will help it render faster and reduce the odds of a browser failing to scale it properly on the fly.

Reducing the file size

Once you've correctly scaled your image, it's time to resize your file via compression to make sure it's as small as possible. Of course, this something that you could take care of on your own by experimenting with compressed file sizes and seeing how they affect the quality.

However, in the day and age of super-sharp retina-display screens, it's better to stick with 100% quality images and instead look to extract data from the file that doesn't need to be there such as EXIF data. It's at this point that things get complicated, and image compression is better left to tools dedicated to this very purpose.

There's a whole raft to choose from (a simple google search will reveal at least ten providers), but for WordPress users, you'll find that the Smush plugin does as good a job as any. Once your image has been rescaled, resized, and compressed, it's time to put it in your article!

Although Google is getting better at recognizing or "seeing" what's on an image, it's doing so through the most vigorous of varifocals. In other words, you're going to need to help out for Google to understand precisely what it's looking at. The best place to start is with the text that surrounds the image, otherwise known as captions.

Remember to check image functionality with each major browser, as some aren't universally supported.

Once you've got the right file name and format, it's onwards to scaling, resizing, and optimizing the image for your website.

Add captions

Captions are an under-utilized weapon in the battle to outrank your competitors. Firstly, they help your readers to gain context when scanning an article. Still not convinced. Does the fact that image captions are read, on average, 300% more than the body of text itself sway you at all? It certainly should do!

The fact that captions keep visitors on a page for longer helps to send positive ranking signals back to Google, often bumping you up a few positions in the SERPs. As mentioned, the text that surrounds an image plays a vital role in providing context and relevancy. Captions are the closest text on the page to the image, so use them wisely to describe your picture.

Alt text / Alt tags

The alt text (sometimes called alt tag) of an image is a space to fill with descriptive text in case of the image failing to display for any reason. This could be because someone who is visually impaired is making use of a screen reader, or because a user has turned off images within their browser settings.

It's also yet another place to tell Google precisely what your image relates to. Make sure to optimize each image with alt text, and make sure to include your target keyword within this space. The more text you can provide relating to the picture, the better for search engines, so never leave it blank.

Add Schema (structured data)

Schema (also known as structured data) is what helps websites display those fancy search results with images, videos, and star ratings. Google has stated that adding schema doesn't have any sway on ranking positions, but they are instrumental in increasing click-through rates, which do count towards better ranking positions.

Adding schema is difficult for the uninitiated; therefore, it's often best to go down the path of a plugin, as was the case for image compression. There are both free and paid-for schema plugins, with the paid-for options offering the most features. If you feel undaunted by adding structured data yourself, here are Google's guidelines for image schema.

Optimize for OpenGraph and Twitter cards

While the debate rages on about how useful social signals are in the context of SEO, it's generally believed that they do. Thus, it makes sense to make your articles as shareable as possible. By optimizing your images for both Facebook's OpenGraph and Twitter cards, readers can easily share your articles with a high-quality picture that is likely to draw in likes, shares, and comments attributed to your website.

This is actually fairly easy to do, even if you aren't a coding genius. All you have to do is locate the <head> section in your page's code and insert the following into it:

<meta property="og:image" content="" />

By doing so, you ensure that your selected image will pop up when users share the article to Facebook, Twitter, and other popular social networking sites. If you're not technically-minded, you can use SEO plugins such as Yoast to achieve the same outcome.

Submit your image to Google through XML image sitemaps

The final step on your optimizing journey is to let Google know that you've got a new image that's worth checking out! Google has always encouraged webmasters to submit sitemaps so that their crawlers can be "guided" to look in the right places when new content is provided.

There are two ways to approach this. You can include images within a traditional XML sitemap (which includes pages and blog posts, for example), or you can submit a separate XML sitemap for images. Popular sitemap plugins usually go for the former method. Still, there's nothing stopping you from submitting a specific image sitemap to increase your chances of ranking an image for a search term.

While you can create your own custom sitemaps, it's perhaps a better use of your time to use a plugin that does it automatically for you. Google XML Sitemap for Images does exactly what it says on the tin and will save you time in trying to understand the complexities of XML.

Final thoughts

Images are often relegated to an afterthought by many publishing articles online. The focus on keywords, content length, heading tags, and meta descriptions often detracts from what can be a powerful tool for improving your position within search results. In many cases, even those that are aware of image optimization for SEO just place the target keyword in the alt text box and leave it at that.

With this guide, you'll be able to take steps to leave your competitors behind by undertaking image optimization for SEO purposes properly. What may only take an additional 10 minutes before hitting "publish" on a post, may add years of increased search visibility for your website. So, make sure to give it a try; you may be pleasantly surprised with the results.

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