How Google Identifies and Indexes Images
So what exactly does Google look at when indexing images? This will help to provide a quick review of what Google assesses before digging into how to optimize images.
- Google can index BMP, GIF, JPEG, PNG, WebP, and SVG image files.
- To learn more about a particular image when Google’s algorithms index an image, Google looks at the written copy on the page where the image was found as well as the page’s title and body.
- Google also considers anchor text (the hypertext link) pointing to the image, the image’s filename, and its alt text (descriptive text about the image).
In addition, Google may use other methods and data points such as the caption from the Image Sitemap.
5 SEO Tips for How to Optimize Images So Google Can Index Them in Search
In order to make it easier for Google to find and index your images, Google suggests the following:
1) Only Use Google-Supported Image Formats on Your Site
As we previously mentioned, the image types Google indexes include BMP, GIF, JPEG, PNG, WebP, and SVG. By only using these image file formats on your site you make it easier for Google to index them.
2) Filenames of Your Images Should Be Descriptive Keywords Related to the Content of the Image
In other words, name your image files something that indicates what the image is, rather than a unintelligible naming convention such as IMG12345.jpg. For instance, for image files of photos of a Tuscan villa name it Tuscan-villa.jpg. Descriptive filenames are also helpful for users who come across your images in search, since Google uses filenames as the image’s snippet in search results when it can’t locate any relevant text on the page that references the image.
3) Use Image Alt Text to Describe Images
Search engines cannot “see” or discern images from their visuals. Therefore we need to use all possible means where available to use descriptive text. Within the structure of a website there is a field for each image called alt text. It’s used to describe the image so that humans can understand it. Similar to choosing an image filename for alt text be descriptive without over doing it. A brief short keyword rich phrase or sentence is sufficient. Two paragraphs is over the top. Using the Tuscan villa example, alt text would be; Casa Ombuto – Tuscan villa (assuming you knew the name of the villa). By the way, Casa Ombuto appears as the first image in Google Image Search for “Tuscan villa.”
The alt text of an image is very important. Alt text functions as a means for visually impaired to determine the context of an image. Alt text was included in websites as a result of the Americans With Disabilities Act. In fact, following ADA guidelines is very beneficial for search engine optimization. For these reasons, Google recommends you be as descriptive as possible, citing the following examples of bad, better, and best alt text for the Tuscan villa image example:
Bad: alt=”” – in this case not using alt text.
Best: alt=”Casa Ombuto a hillside Tuscan villa”
Avoid: alt=”Italian house villa in Italy tuscany. Surrounded by vinyards and Tuscan hillside visitas. Visit these Tuscan hillside retreats and take magnificent images and photos.” This is an example of keyword stuffing or overdoing it and Google doesn’t like to be tricked.
4) Provide Context for the Image in the Page’s Surrounding Text
It helps Google if the text on the page where the image is located mentions the image, too, so always try to reference your images in your text, close to where it lives on the page, using keywords similar to the alt text/filename of the image. Continuing with our Tuscan villa example, let’s say you had inserted that image into a blog post about wine making in Tuscany. To ensure that Google better understood what that image was about, you’d reference it in the text of your blog post near where the image was placed. For example, you might write:
“To the right, check out the exquisite example of the pink paper unicorn one of our customers made using our handmade paper product.”
Google also recommends providing descriptive titles and captions for your images, so consider adding those when relevant.
5) Submit an Image Sitemap
Google encourages website owners to submit what’s called an Image Sitemap, which helps the Google team learn about your website’s new images as well as determine what those images are about. You may already be familiar with Sitemaps in general, which offer a way to tell Google about the pages on your website it might not otherwise discover. In the simplest sense, a Sitemap is a list of the pages on your website.
Similarly, you can also use Google’s image extensions for Sitemaps to give Google additional information about the images on your website. This helps Google discover images it might not have otherwise discovered. In addition, it enables you to identify the most important images on your website. To create an Image Sitemap, you’ll have to add image-specific tags to a Sitemap, or just update an existing Sitemap. To learn more about how to create and submit an Image Sitemap to Google, visit this page for details on how to create one.