Image optimisation
Image optimisation is important in SEO, just like in any form of advertising, from billboards to magazines and leaflets. An image needs to grab a user’s attention and convey the benefits of your product, though not necessarily the features. For example, financial products are boring, so providers focus on images of families together to show how they facilitate a happy home life.
What makes website images different?
Since the end of 2016, more people access the internet on a mobile and tablet device than a desktop. This means website images have to be able to satisfy three sets of screen size, with variations within those three. Different websites handle image scaling differently, but the ideal is that the image focal point remains the centre, regardless of screen size.
You also don’t want the image to take up too much screen size. While the idea of “above the fold” is contentious, you don’t want a visitor to have to scroll past a huge banner to find information. UXers, designers and marketing will typically push for the images to be bigger, while SEOs and developers will want the images to be smaller. It will be a balancing act.
No more than 3 seconds to load
Images also needs to load quickly across all devices. This can be frustrating, as our average internet speeds get faster, but we still need to be able to have images load quickly on mobile phones on 3G connections.
So while we are more and more used to high resolution images and video from the likes of Apple and Netflix, as website owners, we need to make sure images are small enough to not hold up page load. Google has said it thinks websites should launch in 3 seconds or less. While this can be an unrealistic ideal, you really do not want your images to be the reason why your website is behind the curve for your industry. There are other things to consider to make your site faster, such as asynchronous loading of CSS and javascript files, but from a content perspective, having nice, compressed images is the way forward.
In terms of compressing images, I’ve always liked TinyPNG and Pic Resize, but of course if you have access to Photoshop and other editing software, or a skilled visual designer who does, then that will be even better.
Which image format should you use?
Google has stated its image preference with this diagram:
User accessibility and SEO
For the purposes of both user accessibility and SEO, you should give your images an appropriate Title and Alt text, which are image attributes that are part of the HTML code. The title should be logical. For the image above, for example, the title is ‘Image Optimisation Flowchart’, while the alt text is ‘An image optimisation flowchart, showing which image format to use for your website based on purpose, including gf, png and jpeg’.
Get great images for free
If you need a place to source images, all the images on this site are sourced from Unsplash. They offer free-to-use images that are uploaded by photographers and, frankly, puts the likes of iStock to shame. I also like Pexels.
Create a sitemap of images for search engines
As a final note, if you really want your images to be found by Google, you should add an image sitemap. This is similar to the page sitemap discussed here, but only contains images. I’ve yet to find a free tool that does a better job than the Screaming Frog SEO Spider, which is free to use if you are crawling less than 500 URLs. Instructions on how to create the image sitemap using this downloadable software can be found here.