
Best Practice For SEO Image Optimisation
From alt text to modern image formats, learn about the best ways to optimise images to ensure a great experience for your site’s visitors.

Optimising Images For SEO and Good User Experience
Why optimise images for web?
Optimising images can improve your search performance, increase traffic and provide a faster site. It’s important to create a visually appealing site that functions well and engages users.
A good first impression is key. 88% of people won’t return to a site if they feel they’ve had a bad user experience, but a great one can increase conversion rates by up to 200%. Effective image optimisation gives your audience a better experience on your website, including increased accessibility. This will provide potential customers with a greater understanding of your products and services, improving your chances of achieving more conversions.
Best practice for comprehensive image optimisation is often overlooked, but it’s a crucial part of SEO. Learning how to optimise images properly can make a big difference to your website’s overall performance and conversion rates.
Use relevant and good quality images
When choosing images for your site, you should consider how useful they are and how well they actually relate to the page’s text content. Search engines consider how relevant content is on a webpage, so choosing strong, quality, relevant images is a vital part of optimising images for SEO.
It’s also one of the best ways to showcase your brand’s identity. Unique imagery will help you to stand out and ensure customers understand your offering. They influence potential customers’ expectations and, ultimately, their purchase decisions. Too many generic or repetitive images can be off-putting to users, while poor quality images can impact how trustworthy you appear to your audience.
It’s important to keep in mind that ‘good quality’ images doesn’t just mean having high pixel rates. You should ensure images are free from anything that isn’t relevant or that looks unprofessional.
For instance, if your team photo is taken after a coffee and biscuit break, make sure any wrappers or half-empty cups are cleared out of sight. If your business is something like a gardening and patio cleaning service, you might take a photo to showcase the freshly clean and tidy area, so make sure any dirty equipment is moved aside. Always check the background of photos – from healthy and safety violations to old, broken signage, you can guarantee that someone else will spot the things that don’t show your business at its best. Sometimes you can’t see these things until later, so you should crop photos where possible or consider using editing software to remove or hide them.
If your business takes new photos of your work regularly, it is useful to have a basic checklist so people can easily check what to look out for. This will help ensure you always have a wide choice of good quality, relevant images for your site.
Optimise images with descriptive file names
Your images need descriptive and relevant file names that provide search engines with information about the image. Photos uploaded with names like IMG1234.png aren’t telling a search engine anything useful. Use hyphens to separate words (this helps search engines understand the file name better) and ensure they aren’t overly long. Before you upload images to your site, rename files with titles like grey-plastic-garden-dining-table.webp.
If you’re using a CMS like WordPress with a searchable image library, this will also make it easier to find images in the future. e.g. You may decide to write a blog about the best garden furniture and you can simply search for ‘garden’ to find all your garden-related imagery.
Resize and compress images
You should do everything you can for faster site speeds and many websites suffer from slow load times due to unnecessarily large image files. Page speed has a direct impact on a site’s ranking factors, but it can also affect your rankings indirectly. People don’t like using slow websites, so your bounce rate may increase while dwell time is reduced. You should optimise your images for the web by resizing and compressing them before adding them to your site.This can make a big difference to how fast your site loads.
Choose the right format
Your images will probably be saved in standard formats such as JPEG, PNG or GIF. However, a modern file format like WebP can produce much smaller file sizes while also retaining image quality. You can easily convert your existing files to WebP using a tool like Squoosh or with a WordPress plugin.
Use good alt text
What is alt text?
The main purpose of alt text is to provide a description of an image’s meaning to visually impaired users who use screen readers – this is what you should prioritise. However, alt text is also beneficial for your site’s SEO because it helps search engines to better understand what images are showing. It’s what will display to all users if your image breaks or the page loads too slowly.
How to write the best alt text
Your alt text can provide a slightly longer description than a file name. It should convey any relevant visual information to provide a good customer experience for visually impaired audiences.
The best alt text is concise and gives users context for the image – it’s about meaning rather than a pure visual description. It shouldn’t need to repeat content that is already written on the page. You can use keywords within alt text, but ensure they are relevant to the specific image. Bad alt text may be too brief, include irrelevant details or poorly convey the image’s meaning and context.
Bad alt text example:
garden patio.
Good alt text example:
Freshly cleaned patio with a table and chairs under a parasol, overlooking a large garden with well maintained garden borders and raised pond and shed.
How not to use alt text
You don’t need to include phrases like “This is an image of…” in your alt text because screen reader software will automatically detect an image and read out “Image” anyway.
Alt text is unnecessary when it provides no further context, such as a graph or chart where the key information is already in the page text. You don’t need to use any alt text for ‘decorative’ content like background images, icons or section dividers. If an image is truly decorative, alt text creates frustrating and unnecessary noise for screen reader users.
Add captions where appropriate
Captions make it easier for audiences to scan a page to see if it is useful to them. You might find you do not need as much additional information within alt text if it is already described by a nearby caption. They can also offer relevant added context when illustrating news articles or case studies, like the name of the photographer or copyright information.
Optimise images for different devices
While you probably update your website on a desktop, many sites now get the majority of their traffic from mobile devices and tablets increasingly contribute too. Depending on your industry, your target audience may buck this trend, with B2B websites likely to experience more traffic from desktop. However, even within B2B, 20-35% of users come from mobile devices.
Wherever your traffic is coming from, your potential customers may visit your site multiple times before converting. They may start their journey on a mobile and finish it on a desktop or vice versa. 83% of people say that a ‘seamless experience across all devices’ is very important, so it’s vital that you optimise images for different devices.
While image size is even more important for mobile, responsive design is essential for a seamless browsing experience across devices. By making your images responsive, they will load quicker and automatically change to suit different screen sizes and resolutions, whilst still maintaining their quality and proportions.
How to view displays across different devices
You can use a browser’s Inspect Element tool (Dev tools) to quickly preview how your images (and other features) will appear on different devices. Right click on any webpage, click Inspect and you’ll be able to see the inner workings of the website – this is called Developer Tools in Chrome and similar names in other browsers. To open this option simply select the icon in the top left which shows a laptop and mobile phone as shown here:
You can then choose which device you would like to preview by clicking the Responsive section.
This process will look slightly different in different browsers, so you may need to check how to use Inspect Element in different browsers
How can I check to see if my alt tags are pulling through?
Manually
You can use the Inspect Element tool to browse a webpage’s html code, which will include any “Alt” attributes for all the images. You can find all the “Alt” attributes in the <img> tag for each image. Simply use the search box or Ctrl+F to browse the html code. It will look like this:
Browser Extensions
A browser extension can be a quick way of checking whether alt tags are being pulled through when you’re looking at a live page. Some extensions use a hover function for checking alt text, so will only show the details when you hover over individual images. Other extensions will highlight all images on a page and show their alt text status with no additional interaction required. If you already use other extensions that interact with the images, check whether an alt tag checker will interfere with them – you may need to disable them while using your alt tag checker.
SEO Tools
Many modern SEO tools like SEMrush and ScreamingFrog will flag up issues with your website that could be impacting your SEO – including missing alt tags. In SEMrush, this is checked as part of a site audit and SEMrush will highlight the image URL with the missing alt tag as well as the page it’s been uploaded to.
Consider EXIF data
Most modern digital photos will have EXIF data, a way of storing metadata about images, and this is visible to search engines. It can be useful in multiple ways and can make it easier to find files in a photo library. Most of the EXIF data will be technical information about an image, such as the camera’s shooting settings. However, it can also contain more personal information, like the time, date and location that the photo was taken.
The geolocation data might be useful if, for instance, you’re a wedding photographer who works in the West Midlands. If you upload photos from previous weddings in Wolverhampton or Birmingham, this can increase the chance of you showing up for people searching for wedding photographers in those areas. But in other circumstances you might have privacy concerns, so you should consider removing EXIF data from photos with an editing tool.

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