How to Optimise Images for SEO

Image SEO

Image SEO is a great way to encourage engagement with your target audience, you should consider including images in your content to make it more attractive and accessible on the web. This will also boost your rankings in terms of Search Engine Optimisation (SEO).

Well optimised images can contribute to the improvement of your search traffic. Search engines such as Google and Bing will have a better idea of your content, and thus drive more traffic to your site and boost user engagement. This makes it extremely important to take some time to learn how to optimise your images for SEO.

The image optimisation process consists of creating high-quality images in the right format, size, and resolution, ensuring that users understand what they are all about. You do this by labelling your images in such a way that search engine crawlers understand them and the content of your page.

In November 2018, HTTP Archive indicated that on average images took up 21% of the web page layout. The size and complexity of images can negatively impact a site’s performance as images consume the most bandwidth on a web page.

To improve page load times and the experience of users, compress the size of your images in a way that won’t compromise their quality. As stated by the Aberdeen Group study, if the site takes more than three seconds to load, for every additional second it could experience a drop in its conversion rate by 7% and bounce rate as much as 40%.

Bounce Rate
Per Second Load Time

Once user experience and interactions on your site improve, so will its search rankings. This will boost customer engagement, retention, and conversions. Furthermore, backing up your site will be a lot smoother when optimised images don’t take up more space on your server.

Here are effective ways to optimise images for your website

Take some time to resize your images

height and width of an image for image SEO

Image size is different from file size. When talking about image size, people refer to the dimensions of an image. A quick example would be 1024 by 680 pixels. Unlike image size, file size refers to the space necessary to store the file on the server. A good example would be 350 kilobytes.

If you are using a professional camera to shoot images with higher resolution and larger dimensions for your site, these images can greatly slow down your page’s load times. They are good for print reproduction, not for your site. Resize them so they can work well on the site. When doing so, make sure they don’t lose quality.

Pro tip: To find the best image sizes for social media channels, use this guide.

Select the ideal file format

different file formats for image SEO

The most popular file formats, each with its benefits: PNG, GIF, and JPEG.

If you are creating images with lots of colours and detail, use JPEG.

For simple images or images without backgrounds, use PNG.

To create a series of moving images use GIF.

Pick the right compression rate

icon showing magic wand for image compression rates

There is a good reason you should choose the right compression rate: if compressed too high, an image will lose quality even though it will have a smaller file size. A too low compression rate will lead to huge file sizes of your image even though it will preserve the quality.

The best thing you can do is to experiment with various compression rates and file types until you find what works best for you. For great results, use image editing tools, such as Adobe Photoshop, as they let you minimise the file size of your images and provide the option to save for the web, which is extremely useful.

You need to try and find the perfect balance between image size and image quality. Do not use images with bigger file sizes than you need to.

Consider the following popular editing tools if you don’t use Photoshop:

Pixlr (for JPEG optimization)


Affinity Photo




Kraken (bulk compression)

ImageOptim (Mac only)

Here are a few image optimization plugins for WordPress:



WP Smush

Yoast SEO

EWWW Image Optimizer


Optimus Image Optimizer

Test optimisation tools for speed

After optimising your images with the plugins above, test them to ensure they have been optimised for speed.

With these tools, you are good to go. But it’s always a good idea to consistently check your stats as often as possible as your site grows and content changes.

Some tools to use:


Google PageSeed Insights




Rename your file names for SEO

how to name your image file for image SEO

In addition to separating the keywords with hyphens, make sure those words make sense to both humans and search engines.

Avoid naming your files as “dsc0003.jpg”. Rather, rename the file with a clear and descriptive title as in the above example – “blue_mountains_in_springtime.jpg.”

Make use of alternative textimage to show alt text for image SEO

While humans can understand what your image is about right at first glance, search engine crawlers need a different approach. So, make good use of alt tags to help search engine crawlers understand and accurately index your image content.

Using alt tags to describe your files can also help users who are visually impaired to understand your image content better. Your page, which has images with alt text, can still rank well on Google or other search engines even when there is a glitch keeping it from loading properly.
That’s because search engine spiders can still read the alternative text in those images.

You can include your brand-related keywords in the alternative text provided that you don’t add too many of them. Here’s where you can add more details to your images in addition to the ones in the file name — should be from 10 to 15 words.

Add great image titles

good image titles for SEO

WordPress takes image titles right from the file names. So, you don’t have to add any titles to your images if you use WordPress. Otherwise, rename your image title with relevant keywords just as you named your file.

Image titles help boost user engagement and search traffic. They provide more context to alternative text. Since they improve user engagement, they work well with call to action such as “download today” or “buy now”.

Add captions to the images

how to use captions for SEO image SEO

Image captions refer to the words or descriptions appearing beneath images. Although they may not improve SEO, captions positively impact user engagement as they are visible on the page, as opposed to just file names and alt text.

Isaac Justesen recommends writing captions under images not only to add to the user experience but also to reduce bounce rate.

Users like image captions as they provide additional context to the overall content improving the time spent on the page.

Avoid using too many stock images

stock images for use in image SEO

Many online marketers use stock photos. The problem is that, since these images are on many sites, it doesn’t always feel authentic to your brand.  Depending on your budget and timeline original images are generally better.

However, there are several free and royalty-free stock libraries to choose from.  These are a few I use.

Free & Paid Image Libraries:






Make sure your content complements its images

image titles to match content for image SEO

While images are important, they need relevant content to complement them. Search engines look at the copy on your page to determine how relevant the images are.

Include relevant text—whether it be keywords or descriptions—in your images to signal search engines that the images on your page are important and support the content.

Add structured data to images

add structured data for image SEO

As with texts in your images, structured data can help inform search engines that you have rich content; your images will appear on Google images labelled as rich results. You can add structured data to product images and videos as well as recipes. Google supports structured for these visuals.

For example, let’s say you have recipes on your site and added structured data to the images representing those recipes. Google will separate images with structured data from those without the data by adding a badge to the image with the data to inform users that it belongs to a recipe.

Upon adding structured data to your images, they will be labelled as rich results on Google Images. Do this for your images to have high rankings on Google. If you are interested in learning how to add this data to your images in accordance with Google search parameters, use Google’s Structured Data General Guidelines.

Take advantage of site maps

add images to sitemaps image SEO

A site map is a file where your site’s index of web pages is stored. This means your site map is also essential to SEO. Google and other search engines can see your site’s content and thus understand it better through this file.

To take advantage of your site map, you need to include every part of your content in the site map, namely photos, video thumbnail, infographics, memes, and any other important part of your site. Your Image Site Map is an important part of the sitemap index.

When adding image entries to your site map, include the URL location, title, caption, and description of your image as well as license information.

When adding video entries to your site map, include the URL location, raw video file URL, thumbnail URL, title, and your video description.

However, you don’t have to manually add these pieces of information if you are using WordPress to host your site. There are great plugins like Yoast SEO that automatically adds these bits of information to your site map for you. Make sure to add your site map to the Google Search Console—and you will be all set.


Follow these strategies when uploading your images to your site. This way, both users and search engines will love your content, thereby leading to more trust, shares and conversion rates. Happy editing.


As we turn to the digital age, marketers need to stay up-to-date with best marketing practices. Hardcraft Digital provides cutting edge advice and tips for success in an ever-changing world of digital marketing.

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