Besides texts, images are the most important elements on a website. They have the advantage that they are easier to grasp than text and make a web page more interesting and appealing to users. In addition, product images are often decisive for consumers' purchasing decisions in online shops.
Google also rates text content with images better than content without images. Good image content is, therefore, a major ranking criterion for a website. Accordingly, you should definitely deal with the optimization of images on your website (image SEO) as part of the optimization of your website as a whole.
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The aim of image SEO is, on the one hand, to increase the position of your images in Google’s image search and thus create better visibility for your website. In addition, image SEO is also part of the SEO of your website as a whole, since images can generate high-quality content which directly affects the ranking of your website in Google’s general search.
Aspects of optimization
First of all, there are a number of factors concerning a picture itself that you have to take into account for image SEO. These include file size, format and name, image size and format, URL and folder structure, image content, and EXIF data.
- File size: The file size of images should not be too large to facilitate crawling for the Googlebot. In addition, the file size of images also influences the loading speed of your website, which is considered a major ranking factor and should, therefore, be as fast as possible.
- File format: With regard to file format, common formats such as PNG, JPG, or GIF are recommended for images. JPG is more suitable for photos, while PNG should be used for graphics and logos in order to keep the file size of images as small as possible.
- File name: The file name of images is an important factor for the ranking of images in image search. Therefore, it should contain all essential keywords. Of course, these should match the actual content of an image which should be reflected as exactly as possible by the file name. For product images, the use of the exact model designation for the product is recommended. You should separate the individual terms in a file name by hyphens instead of underscores.
The exact description of the content of an image by its file name is not only relevant for a good ranking in image search but also helps Google to thematically classify your website. Instead of a meaningless file name like "image01.jpg", you should use the name "sneaker-adidas-black-model123.jpg" for a product image of a black sneaker by Adidas, for example.
- Image size: Basically, large images have a more positive effect on the SEO of your website than small images (provided that the file size is not too large). The rule of thumb is a length of at least 300 pixels for one side of an image. Too small images like thumbnails don't rank well, but they can still be used if a larger version of the image is displayed when clicking on them.
- Image format: The most suitable format is 4:3, as this is the most frequently clicked format. In addition, you should avoid particularly wide or high formats, as otherwise there is a risk that your image will be cut off on one side.
- URL and folder structure: The folder structure in the URL of an image file should also have a thematic reference to the image subject matter as a supplement to the file name, e.g. www.onlineshop.com/smartphones/samsung/samsung-galaxy-s8.jpg
- Content of a picture: Apart from all the technical characteristics of a picture, you should not neglect its content for image SEO. For example, infographics should be clearly arranged and provide all relevant information. In general, the content of an image must always match the topic of the page. In addition, you should use unique and personal images instead of stock photos, as this is a sign of quality and sets your website apart from your competitors.
- EXIF data: EXIF data is information that is stored in the header of an image file itself, such as the shooting date and location or the camera name. These are often stored automatically by cameras, but you can also add them afterward by image editing programs. Although Google is able to read such information from an image file, it has not yet had any influence on the ranking of a website.
Surroundings and metadata
- Surroundings of an image: The text in immediate proximity to an image (such as its caption) is an important factor for image SEO, as it helps Google to understand the thematic context of an image. It should therefore contain the most important keywords for optimization. This also applies to the subheading above an image.
- Position: Pictures are very well suited to enhance the content of your website, but you should only use them where they actually match the topic of your page and provide value to users.
- Title attribute: A title attribute defines the title of an image, which appears when users move their mouse over an image. The title is, therefore, less important for Google than for users. It should describe the image content briefly and informatively. In addition, the most important keywords for an image should also be included here.
- Alt attribute: An alt attribute specifies the text that is displayed when an image cannot be loaded, e.g. due to server problems or a bad internet connection of users. This is also very helpful for blind people because it is read out by screen readers. In addition, it also helps Google with the thematic classification of an image. Therefore, it is especially important that this short text reflects the content of an image and contains the most important keywords.
Under no circumstances, you should just copy the title of an image, as this would signal to Google that you are not taking great care in designing your website. Furthermore, you should include visual elements of an image (e.g. colors or patterns) into your title and alt attributes, since users often search for such properties (e.g. "black shoes").
- Markups: Markups, e.g. with schema.org, can help to facilitate crawling and classification of an image by search engines.
- img tag: You can insert the image size here to speed up the rendering of an image file.
- Internal linking and repeated use of images: A reasonable internal linking has a positive influence on the SEO of your website. For images, you can do this indirectly by thumbnails, for example. The repeated use of the same image on a website also has a positive effect on its ranking in search results.
- Backlinks: Backlinks are an important factor for the SEO of a website. Websites that are frequently linked to can also have a positive influence on the ranking of the image files they contain.
- SafeSearch: The SafeSearch setting is a default on Google. That's why it's important to check whether images from your website may not be considered safe by Google and therefore may not appear in search results. If this is the case, you should block the corresponding files for crawlers in a robots.txt file as otherwise, you run the risk that Google will exclude all images of your website from search results.
- Longtail search queries: Similar to the SEO of websites, it is often easier to achieve a high ranking for very specific longtail search queries in the context of image SEO.
Use of image SEO
- Visibility: Image SEO leads to better visibility of your image files in Google’s image search. If the images are very relevant for a particular search query, they can also be displayed in the results of the general Google search.
- Traffic: A high ranking of an image in image search can lead to an indirect increase of traffic on your website because the URL of the corresponding page is displayed in search results when clicking on an image. To achieve such an increase in traffic, your image should attract attention in search results and therefore be clicked frequently.
In the past, this type of traffic generation was even easier because the entire website was loaded into an iframe when an image was clicked. Since this is no longer the case, this positive effect has lost much of its significance. Thus, in the context of image SEO, the focus today is less on ranking in image search, but rather on optimizing and enhancing the content of a page and thus SEO of a website as a whole.
Nevertheless, the optimization for image search is not completely unimportant, since many users inform themselves about different product versions in image search. Thus the ranking in image search can have a considerable influence on the purchase decision of users and is therefore particularly relevant for e-commerce sites.
- Easier evaluation of the thematic context by Google: By image SEO, it becomes easier for Google to understand the thematic context of the images of a website and the website as a whole. This, in turn, is rewarded with better rankings.
- User Experience: Another important aspect is that image SEO can also improve user experience, e.g. by reducing the loading time of websites. This is particularly important for mobile optimization, as loading speeds in the mobile sector are usually lower than those available on desktop.