Images make your website and pages more attractive. And you can naturally use them to enrich your content.
As part of your overall content, images provide search engines with vital contextual information.
Consequently, images can also make an impact on how your pages are indexed and ranked by search engines.
To give your online business the best chance of success with search engine optimisation (SEO), you should understand the fundamentals of image optimisation.
In this section of the KAMG SEO Content Hub, you’ll learn about optimising images for search engines and why and how you need to do it.
Let’s dig in.
What is Image Optimisation?
In terms of the overall SEO process, image optimisation is the process of ensuring that you create and deliver high-quality images. It involves making sure that your website and pages have images in the ideal format, size, and resolution to increase user engagement.
Image optimisation also involves accurately labelling images in an effort to make it simpler for search engine crawlers to understand them and the context of your page.
Why Optimise Images
The job of search engines is to find online content and index it so that it can later be matched with any future relevant queries or searches made by users.
And you can improve how much your website content shows up for those searches by using search engine optimisation (SEO).
SEO involves multiple processes that aim to optimise your website and content so that collectively they are simpler for search engines to find, understand, index, and ultimately present to search users.
The result of effective SEO is that people can find your content more often on relevant search engines results pages (SERPs), increasing your chances of getting them to visit your website.
- The simpler you make it for search engines to do their job, the more you increase the chances that your pages will show up on SERPs.
- Also, the better your content and the more optimised it is for SEO, the higher your pages may rank on SERPs.
- And the higher you rank on SERPs, the more opportunities you can get for higher organic traffic volumes from search engines. This then results in more site visitors and greater chances of conversions and profits.
So essentially, you logically need to see to it that Google doesn’t only understand your website’s and pages’ text but also their associated images.
On the other hand, optimised images increase your page loading speeds. As a result, they can help increase user engagement and, consequently, search engine rankings.
According to the Web Almanac by HTTP Archive, one of the biggest contributors to a bloated page (a page that’s oversized in terms of the memory it takes up) is unoptimised images.
Images consume the most size or bytes of any component of your website. So, their size and complexity can have a significant impact on your site’s performance.
When you reduce the size of an image without sacrificing its quality, page load times can improve and, as a result, website visitors’ experiences can also improve.
Ideally, you want your website to load within only 3 seconds, or 2 seconds if it’s an eCommerce store. This is because research has shown that 40% of consumers will wait no more than 3 seconds before leaving or abandoning a site.
Furthermore, because optimised images take up less storage space on your server, site backups will be completed faster.
So, if you want your pages to not only be properly indexed by Google but also rank well on SERPs, you need to put an effort into image optimisation.
The Essential Steps to Image Optimisation
STEP 1 | Optimise Your Image Size
First of all, we must remember that the dimensions of your image and its email file size are not the same thing.
For example, the below image size is 1200×900 pixels.
But if you were to look into the details of the image file, you would find its file size to be 1.77 MB.
Images with a higher resolution and larger dimensions (often created with a professional camera) significantly slow down page loading times. While they work well for print reproduction, they must be scaled down without losing image quality to work well on the web.
Here are the steps to optimising your image sizes.
- Pick the proper image format.
Generally speaking certain image file types are associated with certain use categories.
Here’s an infographic from the 99designs.com article about different image file types and their attributes.
As a general consensus, most agree that the most efficient file types to use for websites are JPG for images that are multicoloured and PNG for simpler images like icons.
However, our SEO experts at KAMG argue that, in general, the file type shouldn’t matter as long as the file size doesn’t slow your loading speed. And that principle is the critical rule to keep in mind.
- Pick the correct compression rate.
Image compression is the process of reducing the size of a graphics file in bytes without sacrificing image quality to an unacceptable level. The smaller file size allows for faster loading speeds for your web pages.
Here’s an example of different compressions of an image from Adobe’s guide on compressing images.
The original, uncompressed image (left) has a file size of 8.9 MB. The file size after compression (right) is 68.34 KB. Image compression reduces file size but also degrades the overall quality.
By comparing the insets from both images one can see how much detail has been lost.
When an image is overly compressed, the file size is reduced but the image quality suffers.
When using a low compression rate, the image quality can remain high, but the file size can also remain unaffected.
Ideally, one should try different file types and compression rates to see what works best for each image.
Many image-editing software programmes, including Adobe Photoshop, have a Save for Web option that automatically reduces file size while optimising image quality.
If Photoshop is not an option, there are other tools that could be considered.
Image Optimisation Tools
- Pixlr (JPEG optimization)
- Affinity Photo
- Kraken (bulk compression)
- ImageOptim (originally made for Mac)
- JPEG Mini
WordPress Image Optimisation Plug-ins
Optimisation Checking Tools
These are tools to check if your website’s page loading times are fast enough after you’ve optimised your images.
STEP 2 | Optimise the File Names of Your Images
Choosing the appropriate file name is critical for your page’s SEO and ranking in image SERPs.
To maximise SEO power, name any image file before uploading it with relevant, descriptive text. Try to include the target keywords of your page if it makes sense within the page’s context.
Separate each word of your image file name with hyphens (-).
Avoid using underscores (_) because search engines will not recognise them and will not be able to “see” the words individually.
“A cat is excited to get a training treat” to describe the above image is better than just using the keyword “cat training.”
So a good file name for the image could be “cat-excited-for-treats-during-cat-training.”
STEP 3 | Use Alt Tags
Your readers may quickly understand what a picture is about, but search engine spiders often require additional information.
ALT tags, also known as ALT attributes, are “alternative text” for images. ALT tags are used to describe an image or what it represents.
ALT tags become part of your pages’ and posts’ codes.
Here’s the alt text to an image used on a dental clinic’s page. It says “image of a boy who’s about to wear a mouthguard.”
One of the primary functions of ALT tags is to assist visually impaired users who use screen readers while browsing. It is also what is displayed in the place of an unloaded image.
And the tags are also used by search engines to better understand what the image is about in the context of your page or post.
So, without alternative text, search engines cannot accurately index your image content.
To increase search engine visibility, include brand-relevant words in your alt tags while ensuring that your text properly describes your image. Just avoid keyword stuffing, i.e. deliberately repeating keywords again and again on your page and its elements.
Here are tips for writing ‘good’ alt text.
- Describe in detail what’s in and going on in the image.
Think of how you can accurately describe the image to a blind person in as few words as possible.
- Only use keywords if they help accurately describe your image.
Google is already smart enough to know what your content is about even if you don’t use keywords directly. Simply try to describe your image well and if your keywords fit, then proceed; otherwise, you can drop it.
- You may not add alt text if the image is accompanied by a caption on the page.
You don’t have to repeat yourself.
If your image is already properly captioned with a displayed text, it can already serve as your alt text although in a different format.
The less text your page has to load with, the faster your page loading speed will be.
- Don’t add alt text to decorative images.
Images that are part of your content’s context are called illustrative images. They are images that help the reader understand your page or post.
You should add alt text to illustrative images only.
Images that are simply there to make your page look nice are decorative images.
They are not truly part of your content and it would be a waste of loading speed to add alt text to them.
- Include text that’s in the image.
Transcribe whatever text is in the image.
Think about how a text-to-speech machine can help a blind user understand a text-heavy image like an infographic. And the solution would be to transcribe the text so that the machine can read it to the user.
STEP 4 | Use Descriptive Image Titles
If you use WordPress to host your website, the image title is usually derived from the file name. So you can sometimes leave it alone if you are sure that your file names are already SEO-friendly.
If you don’t use WordPress or the title doesn’t adequately describe the image, rename it just as you would file names.
STEP 5 | Describe Your Images With Your Copy
Acknowledge your images and talk about them in your content.
The most straightforward way to do this is by captioning them.
Image captions may not have a direct impact on SEO, but they are visible on a website page, unlike file names and alt text.
As a result, they can improve the user experience.
Aside from using captions, ensure that your images and text complement each other.
One thing to keep in mind (especially for blogs or posts) is that you shouldn’t simply put up an illustrative image and not talk about it with your text. You want your reader to contextualise your image so describe it on your copy.
Images on service pages usually are treated with alt text instead and not written about on body text.
STEP 6 | Use Original Images
Stock photos are acceptable, but they will not necessarily help your search rankings. This is because other websites frequently use the same images.
Similarly to how unique written content improves SEO, it’s a good idea to upload unique images whenever possible.
STEP 7 | Include Image Structured Data
By including structured data on your pages, search engines can display your images as rich results.
Rich results are Google Search experiences that go beyond the standard blue link. They are driven by structured data and can contain carousels, images, or other non-textual elements.
Structured data is supported by Google Images for product images, videos, and recipes.
For example, if you have recipes on your site and add structured data to your images, Google can add a badge to your image indicating that it is associated with a recipe.
The following snip of a SERP for the search words apple pie recipe shows rich results.
To ensure your content is displayed as rich results, follow Google’s General Structured Data Guidelines.
STEP 8 | Include Images in Your Site Map
A site map, according to Google, is “a file where you can list the web pages of your site to tell Google and other search engines about the organisation of your site content.” In other words, it’s a file that contains a map of the content of your site.
Site maps are an important part of SEO because they inform search engines about all of your site’s pages.
Include every image like infographics, memes, photos or video thumbnails, in your sitemap to ensure that search engine crawlers notice them.
Include the title, description, URL location, caption, and licence information for these image map entries. Include the title, description, URL location, thumbnail URL, and raw video file URL for video entries.
If your website is hosted on WordPress, you can use Yoast SEO, which will add your visual content to a site map automatically.
Optimising your images can contribute significantly to your rankings and traffic.
Images are part of your overall content, and if Google and other search engines are to show your pages to searchers, they have to be appropriately indexed.
The key here is to make it as simple and quick as possible for search engines to find and understand your website and its pages. Done right, your SEO can increase how many people come to your website and give you more prospects to convert and profit from.