How to optimise images for SEO: 7 must-know tips!

Reading Time: 6 minutes

Image optimization is making sure that you follow SEO guidelines for the images you use on your website. This is important for anyone with a website, but especially those with an e-commerce site. You want Google and other search engines to rank your images.

From reducing image file sizes so that they don’t impact on site speed, to how you name your image files, and what file type you choose, optimising images might take a little time but is worth doing properly.

Here’s a sneak peak of my 7 tips for image optimization:

Image file names

Alt attribute optimization

Image file size reduction

Appropriate file types


Image sitemaps

Limit use of decorative images

(plus keep reading for my bonus tip!)


Click here to get your free Image SEO Checklist so you know exactly what to do with your photos for SEO




If you already have lots of images on your website that you haven’t optimised for SEO, I would strongly advise against making any changes to your existing images. Any changes you make now could impact on your SEO, especially if your existing images already have link juice and authority.

The best thing to do would be to implement the below suggestions with any new images that you add to your website.


Image file names

Image file names are an easy way to improve your on-page SEO.

Remember the following:

-Use keyword descriptive language

-Don’t use stop words (such as a, in, the)

-Use hyphens, but don’t use underscores (Google doesn’t recognise them!)



Use keyword descriptive language

don’t use names such as image1 or shoe. Be more descriptive if the image is of your product- what colour is it? Your brand name? The product name?

SEO optimising images








Poor example: greenshoe.jpg

Better example: Converse-Chuck-Taylor-Mens-Green



Get rid of default names that your camera gives each image- these won’t help your images rank on Google. The image file name gives Google’s bots clues as to what the image is. Image0001 doesn’t tell Google much!

Image file names are also important because they will help the customer find you. When your customer is searching for your product, think about what words they would search. In the Converse example, possible search queries could be:

Mens Converse green shoe

Chuck Taylor green ladies shoe

Converse green shoe

The best way for you to find out what keywords your customers are using in Google, is to have a look at your Search Analytics in Google Search Console. Look at the queries that contain your products to find out what keywords your customers are searching by.

Remember to use your keywords where possible but don’t go overboard!

Don’t use stop words

Stop words aren’t necessary!

Poor example: a-green-shoe-on-a-shelf.jpg

Good example: green-shoe-shelf.jpg

Use hyphens, not underscores

Google has actually stated in the past that underscores shouldn’t be used as they aren’t good for SEO- Google bots can’t recognise them. Make sure you use hyphens instead.


poor example: filename_using_underscores (Google reads this as filenameusingunderscores)

good example: filename-using-hyphens


Alt Tag optimisation

What’s an Alt Tag?

An Alt Tag is alternative text used for your image for when a browser can’t render the image properly. Often you can see what the alt text is by hovering your mouse over the image.

Alt tags help improve your site’s SEO, especially if you use your keywords strategically. This will help you rank better on search engines. For e-commerce websites, alt attributes is one way to ensure that your product images are found on Google.

You need to add an alt tag to each image on your site. Here are some things to remember when adding alt tag:

-Including product model or serial numbers if there are any

-Use keywords strategically- don’t keyword stuff but use them naturally, just as you did with image file names

If you have multiple photos of your products (for example from different angles or different colours), make sure you differentiate each alt tag by including information about the angle or colour.

Going back to our Converse example, if I took photos of the shoes from the front and back, I could do the following:

Image file name: Converse Chuck-Taylor-Green-Shoe-Side.jpg

Alt Attribute: Converse Chuck Taylor Green Shoe Side

This tells Google and users that the photo is the front of the shoe. Do the same with the back of the shoe and replace the word “side” with “back”.


Reduce Image File Sizes

Large image file sizes slow down a website, which impacts on the user experience and your SEO. Your users are more likely to leave a site if it’s taking too long to load due to images or other speed issues.

Google favours websites that load faster and give users a better experience. Its algorithm penalises sites that take too long to load.

The good news is there are simple ways to reduce the image file size.

If your site runs on WordPress, download the Smush plugin which reduces your image file sizes without compromising the quality of your images. It’s the most popular plugin for image compression and is very easy to use. The best thing is you can set up Smush so that in future it auto compresses images when you upload them on your site.

Other plugins include EWWW Image Optimizer, Hammy (which is great for increasing mobile speeds) and SEO Friendly Images (which also edits your alt and title tags).

alt attributes optimising images for SEO

Choose Appropriate File Types

Your image file type will impact on your site speed, so choose wisely.

JPG, PNG and GIF file types are typically used for images however each of these has a different impact on file size and page load speeds.

JPEG images are the standard used, as they can be compressed into a smaller file size without having too much of an impact on the quality.

PNG images are increasing in popularity. They are great for complex images with lots of colours however their file sizes are larger than JPEGs. With PNGs, you can choose between a PNG-8 file size or a PNG-24 file size but this will change the quality of the image. It’s better to use PNG-8 over PNG-24.

GIFs are also popular but are better suited to decorative images, animation and thumbnails, and not photos. This is because the photo quality reduces in order to remain at the low file size.

Summary- For photos (especially product photos), JPEG and PNGs are best. GIFs are great for decorative images, thumbnails and animations.


Manage Your Thumbnails

Lots of e-commerce sites use thumbnails for their products, to give users a quick look at products without taking up too much space on the page.

While site owners might think this is good for user experience, thumbnails impact on page load speeds, which ISN’T good for user experience (or for SEO!).


Make thumbnail file sizes as small as possible, even if this sacrifices image quality. This helps increase page load speed.

Change your thumbnail’s alt attribute so that it is very different to the original image’s alt attribute. You don’t want your thumbnail being indexed over the original larger image!


Image sitemaps

Image sitemaps tell Google about the images on your site, and helps users search and find your images on Google. You use sitemaps to let Google know which images to crawl and index on each page.


Limit use of decorative images

Decorative images such as borders, backgrounds and buttons can impact on your page speed and SEO. Buttons are common for e-commerce sites, but limit the use of borders and background images. Instead, use CSS styling as much as possible.


In summary

For SEO best practice, do the following with your website’s images:

Use descriptive words and keywords in your image file names

Don’t use stop words or underscores in your image file names

Strategically use keywords in your image alt tags

Reduce image file sizes through compression (eg Smush plugin)

Use appropriate file types- JPG is best, and PNG-8 is also suitable

Reduce thumbnails even if it means sacrificing image quality

Create and submit an image sitemap

Limit the use of decorative images


Bonus tip:


I recommend getting into the habit of creating optimised image titles when saving or downloading images on your PC or phone. This will not only help you later on when you upload the image onto your site, but it will also help you organise your images on your laptop or phone!

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Nat Alleblas- SEO Sleuth: helping copywriters, marketers and web developers with their SEO needs. When she's not slaying SEO, Nat can be found with her head buried in a book or is smashing out a spin class. But not at the same time. Loves eggplant lasagna.

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  1. Alana May 3, 2018
  2. Margaret Enever April 27, 2019
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