Image SEO refers to that part of on-page search engine optimization which primarily relates to image files. In practice, it is usually referred to as image optimization. The objective of image SEO is to increase the visibility of a website in addition to better placement in the Google Images search. Moreover, image SEO will improve the TF*IDF ratio. Images usually get optimized for searches, since Google has the world’s largest database of images, and has an estimated 10 billion images. Image search engine optimization considers all elements of a graphic such as file name, size or even positioning on the website.
A website is comprised of many different elements. Some of these are visible for the users and others, such as the source code, are generally not. Images are the major visible components of a website next to the text. In the area of e-commerce, for example, the quality of product images and design have a decisive influence on the purchasing behavior of customers. Large stores, such as Zalando, routinely optimize their images. Visible and invisible factors play an equally important role in image optimization.
While the goal of the conventional search engine optimization is oriented toward a website, image SEO aims to achieve a good ranking for the image file. However, within the scope of a holistic search engine optimization, image SEO is more important.
Aspects of image SEO for search engines
Similar to on-page optimization for websites, image SEO has different levels, which can be worked on and optimized – the visible level, the meta level, and the image plane itself.
Search engines such as google may have improved their ability to recognize images through artificial intelligence and machine learning, but they still cannot read all types of image content. For this reason, the context in which the image material is integrated as well as the meta elements are very important for image optimization.
The following aspects apply to the optimization of the image itself:
- File size: For an image url or file to be included in the index more quickly and easily by the Googlebot crawl, it is advisable to work with moderate web-optimized file sizes. Thus, high-resolution images of exteriors with more than 10 megabytes should not be used. At the same time, the size of the image file has an important influence on the page speed of a website. As the loading time of a website counts as a ranking factor, the optimization of the image file size is therefore very important.
- Filename: This plays an important role for the subsequent ranking in the image search. It should accurately represent what is seen on the screen. At the same time, the picture will be considered in the entire context of a website. For Google and other search engines, the name offers an important orientation point in recognizing the topic of the website.
Example: An image of a fir tree. Filename: fir.jpg
Additional data is added with dashes.
Example: Image of a green tomato. Filename: Green-tomato.jpg
- Image Size: It is commonly agreed upon in SEO circles that small images such as thumbnails or previews do not have much of a chance to rank well in the images search. A benchmark of a minimum 300 pixels has been established for at least one side of the image.
- Image format: Images which are displayed in landscape or exact 4:3 format are clicked more often.
- Source: The URL of the image plays a role in image SEO. It is advisable to use a thematically relevant folder structure.
If you want to promote the indexing of image files, you can save all image URLs in a separate XML sitemap and upload it to the Google Search Console.
The following aspects should be considered when embedding an image and relating meta data:
- Content: the content surrounding an image is important for its ranking. The use of relevant keywords is especially a factor.
- ALT attribute: The classic function of alt tags is to describe an image in case it cannot be displayed in the browser due to technical problems. Therefore, the alt tag should accurately reflect the content of the image and contain the main keyword.
- Title tag or image title: The meta title should also be used to fit in a relevant keyword. The title is however primarily for the improvement of usability and less as an SEO factor.
- Markups: with the help of schema.org and other markup languages, Images can be overlooked with structured data which the search engines can read. This data makes it easier for bots to crawl and order.
Linking plays a role in SEO images as well. The following factors must be taken into account if you want to achieve a good ranking:
- Strong internal linking: This can be done “hard” or indirectly via thumbnails. Again, moderation should be applied here.
- Multiple uses: In this case, images SEO is complementary to content SEO, because the multiple use of an image with the same meta data will benefit ranking. This also applies to exact copies.
- Backlinks: These do not affect the ranking directly, but nevertheless should be taken into consideration, because the more trust a website has, the more likely it is that their images rank well.
Another important factor in image optimization is that the subsequent ranking for a specific keyword or a group of keywords, of course also depends on the competition. It will consequently be more difficult to rank well with the image of a celebrity under their name if that image has been optimized for the term “la la la” in the image search.
The benefits of SEO images can be outlined in the following bullet points:
- Strengthening of visibility: as images of high relevance can be shown directly in the organic google SERP, websites with optimized pictures can increase their presence in the search results.
- Indirect traffic boost by good ranking with images: if images are clicked on in the google images search, more users will come to the website. Therefore, traffic can be increased with image SEO.
- Possibility of top rankings on universal search: it can happen that a website can't be found with the URL in the top rankings, but with an image.
- Improvement of topic relevance: if pictures are described with important tags, the entire thematic context of a website can be improved. Therefore, the chances of being able to target better rankings in the google search increase.
- Improvement of usability: if images are condensed appropriately and are of high quality, the usability of the website increases. Condensing an image is important above all within the scope of mobile optimization, because smartphones often don't have a high band width when out and about. Large image files can cause the page to load slowly.
- More traffic for e-commerce websites: if potential customers search for a product, they often use image search. If a company is present there because of image SEO, the changes increase of more users, and therefore more conversions.
Optimized image files do not support a website only in terms of search engine optimization. For example, adjusted file sizes reduce the loading time of a website and thereby affect the user experience positively. Optimized image data is also ideal in terms of accessibility, to give blind users the opportunity to learn all the content of a website, for example.