Images can take up a large amount of space on your website, so it’s important to optimise their size in order reduce the effects on page speed. Images can also be optimised to help boost your website’s ranking in search engines. I will explain some of the techniques you can use to optimise images for SEO and how this can impact your website.
Using keywords in image file names is one of the easiest and often overlooked opportunities to optimise images. You could include one or two keywords in the file name which are relevant to the image, but not too many. Stop words like a, the, in and of should be left out and the file name should still provide an accurate description of the image. It's also good to include to name of the company in the image file name.
Image alt and title attributes are another simple way of optimising images. Alt text, primarily designed for visually impaired users, is displayed in place of the image if it cannot be shown or is taking too long to load, and title text appears when visitors hover over images. Most major search engines are text-based, so they cannot read images; if there is no alt or title text, those search engines will see the images as empty space, which is not good for SEO or accessibility.
Alt text should be short but descriptive. Try to describe the image as specifically as possible, using keywords but avoiding keyword stuffing (adding too many keywords). Don’t include ‘image of’/ ‘picture of’ as it is already assumed that you are describing an image. Title text should also be kept short, include a keyword and provide additional information about the image.
Non-optimised: img src="/images/gallery/altitude_lofts_loft_conversion_farnham.jpg" alt=""
Optimised: img src="/images/gallery/altitude_lofts_loft_conversion_farnham.jpg" alt="loft conversion with ensuite in farnham" title="Ensuite Loft Conversion Farnham - Altitude Lofts"
Choosing the right file format, size and dimensions is key to image optimisation. In terms of format, JPEGs are usually more SEO-friendly than PNGs as they offer better compression levels. Logos and other high-resolution computer-generated graphics can typically also use the SVG file format. There are next-gen image formats to consider too: JPEG 2000, JPEG XR and WebP have greater compression levels and load faster than older image formats.
The actual file size is the most important aspect of this optimisation method as this directly impacts page speed. Images should be saved at under 100Kb or less when possible, and at a quality of around 50-70% instead of 100%. The quality should be good enough that the image doesn’t look distorted or blurry. If you need to use a larger file size for whatever reason, you can save images as progressive JPGs so they gradually turn less blurry as they are being loaded. You can also use compression tools like TinyPNG to reduce file size.
When changing the dimensions of images (height and width), you should ensure that they are not wider than the most popular large desktop screen resolutions (1920 x 1080 e.g.). Take a look at these browser display statistics for more information on popular browser sizes. You should also make sure that your CSS makes your images responsive, adjusting to screen or window size – this is a key part of mobile optimisation.
Overall, image optimisation is key for improving page speed, SEO and user experience. It’s not just important for brand new websites, but existing ones too. If you have any questions about this topic, or would like to know more about our SEO services, why not get in touch?
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