How to improve SEO by optimising images

Images aren’t just for making web pages look pretty and they can also illustrate important points, show charts, step-by-step guides and much more. They are an important factor for SEO too.

Images are an essential part of any web article and they break up the text and make it look more exciting. There is nothing visually worse than 1,000 words of text all on its own.

People can share your post’s images on social media and they could be pinned on Pinterest, posts can be shared on Twitter and Facebook, and images included, and so on. Shared images that link back to the posts on your website will boost the site’s SEO.

You should aim for at least two or three images for each post, and sometimes more depending on the subject. An image every 3 to 400 words is good, but it is not a rigid rule.

The image problem many people face

A common problem that often occurs is that a website owner will sooner or later discover that their website is slow. Pages take a long time to load and it is tedious to navigate. Traffic from mobile sources like phones, could be low too.

I’ve seen web pages with several 2.5MB+ images, which is huge. In many cases the cause is large high resolution images that have been inserted into posts.

Panic then sets in as the owner realises that they have a serious problem with images dragging down the site speed. This affects SEO and speedy sites are more likely to rank higher than ones that are very slow.

Large images in posts are not too bad on a desktop PC with a fibre optic connection, but these days a lot of people are browsing the web on mobile phones and tablets.

These are slower devices with limited processing power and memory, and sometimes poor internet connections.

If you use large images then your site might be poor on phones and might not rank as highly in Google searches, particularly mobile searches.

Google likes web pages that are fast and lightweight, and work well on phones and tablets.

1 Optimise your images

It is best to avoid the problem in the first place. Images should be created in a photo editor or created elsewhere and then loaded into a photo editor. Many people use Photoshop and it is a brilliant program, but it is also expensive, requiring a monthly subscription these days.

Photos taken on your phone or with a digital camera are often 2,000 or even 3,000 pixels wide. Photos on web pages rarely need to be more than 1,000 pixels wide. This means that they can be resized and shrunk by 50% or more, with huge savings in the file size.

GIMP is a free alternative to Photoshop that is fine for optimising images for the web and it works on Windows PCs and Apple Macs. Paint.NET is another free and useful photo editor for the PC. Images can be opened in the Preview app on the Mac and if you go to Tools, Adjust Size, you can shrink large images. GIMP is better though.

Every photo editor is different, but in GIMP you would select Image, Scale Image. Then set the size.

Resize images in GIMP to shrink the size

Then go to File, Export and save the image. If you tick the box, Show preview image in window, it shows the file size just under the quality slider.

Lowering the quality reduces the file size. It is surprising how much the quality slider can be lowered without it being noticeable.

Setting it to 60 or 70 will shrink the file size, but with just a tiny lowering of quality. In fact, most people will not notice. Yet you make huge savings with the file size.

Use GIMP to optimise images for the web - add a little JPEG compression

This image was originally 668K and as you can see in the screenshot above, the new file size will be 115.1K. That is one sixth of the original size. The page will load faster and this is important for SEO, particularly for mobile SEO.

It depends on the WordPress theme, but some designs (this one for example), can only fit images up to 600 pixels wide. If I resize a large photo to 600 pixels, the maximum that will fit, and add a little compression a 1MB file can become 50k. What’s more, it only takes a minute to do in a photo editor.

2 Resize old images with plugins

If you have got yourself into a mess by uploading lots of large high resolution images, there are some WordPress plugins that can solve the problem.

WP Smush Image Optimizer, ShortPixel Image Optimizer, and EWWW Image Optimizer will go through all the images used on your website and reduce the size. Some people say their web pages load in half the time afterwards.

Instead of relying on plugins to fix problems, make sure images are the right size in the first place using a photo editor. It is best to keep plugins to a minimum.

3 Add image descriptions

Every image you use on your website should have a description. When search engines index your website and find images, the description tells them what is in the images.

Here is an example:

A green steam train at the railway station in Porthmadog, Wales, UK

You can instantly see that this is a train, even though the angle it is shot at isn’t the best. Can Google, Bing or Yahoo! tell what it is? They need to be told what is in the image.

Select Media Library in the WordPress sidebar and the images your site uses are displayed. Click an image to select it and on the right are some boxes where you can add descriptions.

Fill in the Title and Alt Text boxes. The Alt Text is the more important of the two and it is used to describe the image. Image captions can help with SEO too and it enables you to provide an alternate description of the image.

Here you can see that the title is “Steam Train” and the description is “A green steam train at the railway station in Porthmadog, Wales, UK.

It is easy to see why this is so good for SEO. When someone searches for ‘steam train’, ‘Porthmadog’, ‘railway station’, or ‘Wales’, this page will appear in the search results. (Sorry if you came here looking for steam trains!)

The image description is packed with keywords and useful information for search engines and your posts are more likely to appear in search results.

Every image you post should contain information like this.

The length of the text that can be entered is not limited, but it is best to keep it as short as possible while fully describing the image. It is great for SEO.

That train description above is a good example and there are 12 words. More could be added, but descriptions should be natural and overly long descriptions that are stuffed with keywords might be penalised and have the opposite effect on SEO.

4 Choose filenames carefully

Filenames also help search engines to work out what an image is all about. If you have a post on your website about cats for example, you could have pic1.jpg, pic2.jpg and pic3.jpg.

Those filenames do not help search engines or SEO ranking because they could be anything. How would a search engine know that the pictures were of cats?

Use filenames that are descriptive, but not too long. In the cat post example, you might have filenames like tabby-cat.jpg, ginger-cat.jpg and cat-sat-on-a-mat.jpg.

Those filenames are good for SEO because they describe the image. When someone searches for cats or cats sat on mats, the images will turn up in the search results.

The filename is set when an image is created and before it is uploaded to your website.

Action points

  • Large images are slow to load and bad for SEO, particularly mobile
  • Small images are fast to load and good for SEO, particularly mobile
  • Shrink images in a photo editor and apply a little JPEG compression
  • Add a plugin to optimise your site’s images, but only if you need to
  • Add descriptions to images to help search engines and boost SEO
  • Keep descriptions short, but sufficient to fully describe the image
  • Use short, but descriptive filenames for all images


Go: Courses Home Page