Optimizing images

Images optimization for SEO

Images are an integral part of all websites. The message they carry can be as powerful as texts & videos. The same is for SEO relevance of images in SERP. It’s been a while since Google introduced graphical elements in the result pages, but many websites still struggle to utilize the full potential of images to generate organic traffic. The optimization process can be a lengthy and difficult task. Many factors are to be considered. The details are often omitted, although it is just as important as other SEO aspects. Proper optimization of graphic files is not limited to checking their size, resolution and format. The description of the photos is also of great importance. More than that, correctly filed alt attributes of an image are one of the most important ranking aspects in modern SEO.

Why is it important to optimize images for SEO?

Image optimization, like any other SEO procedure, is aimed to improve website rankings for important keywords.There are many additional benefits that Image SEO can bring to the website overall quality. More than that, together with Structured Data implementation, can boost the attractiveness of Your search results.

Improving Core Web Vitals

One of the main benefits is the reduction of website loading time. Well optimized images can make a huge difference especially when the user is using a mobile device. CWVs are considered a factor influencing rankings in Google.

Google Images

There’s a lot of different images on the web & search engines are very selective in terms of what content will be shown in the result pages. A well-crafted description of the image on your website can significantly increase the chance for it to be displayed & generated traffic. Most of the eCommerce traffic is generated with queries for particular products.Users often search for a given item by finding the appropriate product photo. In this way, more users may be redirected to our website by searching for images on Google.

Image relevance on the page

Google is treating graphical content similarly to textual in terms of usability for end users. Having images that are well optimized & relevant with the whole page content is something that the search engine’s algorithm will appreciate. Optimizing images will have a good impact on our bottom line SEO results.

Optimization of images for SEO – the recipe

Image optimization for SEO should be a process, to make it as simple as possible. You should know the dimensions of product photos, blog post images, thumbnails, etc. prior to preparing a set of graphics for Your website. Assuming that You know this already & have the full library of images cropped, let’s start with a simple, few step rule book:

File name

The file name should not be a random mixture of letters or numbers. You should use words that describe the picture or the page where this image is placed. The name should be concise and describe exactly what the picture is about using keywords. You can use numbers to make You life easier, especially if You have two similar images on one page.

In addition You should be avoiding spaces and underscores in names – if your filename contains more than one word, separate them with a hyphen (-), it is easier to read for bots.
Examples of good filenames:


Examples of bad filenames:


The “alt” & “title” attributes

This is an alternative description of the photo that will be visible in a case Your online connection is too slow to load images. It’s also used by accessibility software & search engine robots to see the content of an image. The Alt attribute should contain a short information of what is on the image, preferably described with keywords relevant to the page.

You should treat the alt attribute more like a short description tag, than the list of keywords. Do not use semicolons to list them.

The content of an image’s “title” attribute is what the name suggests… a title of an image & is displayed when you hover the cursor over the photo.

Size of the graphical elements

This is the point when the rule to remember is “less is more”. The smaller the size of the image, the faster and more efficiently the website will work. The factor that You will need to evaluate is the image quality. You need to find the right balance between the image quality & size.

To check the optimization of your photos on the website, you can use Boostsite. The tool will help you to find the images that are not optimized & The build-in tool will generate a free to upload library of correctly compressed images… solving the problem.

Choosing the proper format

It is worth noting that different graphical formats have different use in web design. Some of those are just better suited for SEO.

  • JPG – is the most universal and recognizable format that all browsers can handle. Nice compression makes it the most suitable for SEO purposes.
  • SVG – this is the format most often used for logos and icons, they are mostly transparent graphics
  • PNG – this type of format has improved quality & using it makes sense in situations where we want to keep the background transparent. Nevertheless the size of PNGs is generally greater than JPGs.


Next-generation image formats

For some years Google has been experimenting with introducing new, next gen image formats. In 2014 YouTube started using WebP format in the thumbnails, as they load faster. Next generation image formats are all about the quality vs size dilemma. The end result is that those types of images can load faster & starting to be a standard in the modern online world.

There are three formats worth mentioning:

  • WebP – encoding images in two modes – lossy and lossless – has better compression efficiency than regular JPG, but is not compatible with every known browser. The MIME type (two-part identifier for this file format) is image / web.
  • JPEG2000 – more effective than standard JPG, also not compatible with all browsers. The extensions used in JPEG2000 are: .jp2, .jpx, .jpm, .mj2 MIME types: image / jp2; image / mj2; image / jpx; image / jpm
  • JPEG XR – or JPEG extended range – developed by Microsoft was supposed to be a replacement for JPEG2000 and JPEG, but closer to WebP. Lossless compression is possible and has alpha channel support – graphics transparency. Its extensions are: .jxr, .hdp, .wdp; MIME types: image / vnd.ms-photo; image / jxr

Automated images optimization

As mentioned before, there are tools that make the process of Image SEO easier. We encourage you to use the Boostsite tool, where you will get all the information about your images & image compression tool is available as well. If You use WordPress, there’s a variety of plugins that will get the job done:

  • Smush
  • Optimus
  • EWWW Image Optimizer
  • ShortPixel Image Optimizer
  • Compress JPEG and PNG Images
  • Imsanity
  • Imagify
  • reSmush.it
  • Kraken Image Optimizer
  • WP Compress

Image SEO – consistency is key

The whole process may seem a lot at first, but this time the bark is worse than the bite. Remember that the full Image SEO is one time job & there are tools to support You. If You incorporate the process in your daily routine of uploading new content it will not be very painful. However, the benefits can be huge, opening a new stream of quality organic traffic to Your website.

Co-author: Alicja Moczko

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