This is day 4 of 9 in our series on optimizing your web content to take advantage of the opportunities presented by Google's new Universal Search results pages. See the list at the bottom of this post for a schedule of posts and links to previous posts about Google Maps, Google News and Google Video/Youtube optimization tactics.
A picture is worth a thousand words, especially when it comes to search engine results pages (SERPs). Google has included Google Images results for quite a while atop their normal web search results, but the new Universal Search brings this practice to the forefront and forces online marketers to think about optimizing more than just their web pages. High-ranking images can deliver tons of traffic to a site for popular keywords, without having to compete against the top-ranking organic web search results. Image search is not nearly as competitive as relatively few sites are aware of it and even fewer are doing anything about it.
Similar to video, images present problems for search engine crawlers. They can't interpret the meaning of an image by itself and must rely on signals around the image file (meta data) to supply context. The following list of image optimization tactics should be used to improve the accessibility and crawlability of images on your site.
1. Use descriptive file names - Identify your target keywords and name your images accordingly. A great example would be "hubble-telescope.jpg" instead of "img10402.jpg" or "hubtel.jpg".
2. Add an "alt" tag for each image - This is accessibility 101. Many web users (visually impaired and those with slow connections) surf the web with images turned off or use screen readers. An alt tag will display text where the image would normally appear, or when a user hovers their mouse over an image. Search engine crawlers view images much the same way, a big blank space with (hopefully) some accompanying text to indicate the contents of the image.
3. Provide a caption - Many times, a search engine crawler will examine the text around an image to look for clues to its meaning. Providing keyword-rich captions or descriptive text nearby will create additional context.
4. Optimize the rest of the page where the image is displayed - A large factor in ranking image results is the relevance of the site and page it is hosted on. For example, an image hosted on harvard.edu will most likely rank higher than the exact same image on this site because harvard.edu has significantly more PageRank, credibility and authority. That being said, utilize SEO best practices throughout your site and your image rankings will benefit. This includes having unique, descriptive title and description tags on each page, properly formatted and accessible URLs, relevant content and lots of quality links.
5. Add image tags where possible - If your images are hosted on sites like Flickr.com, use their tagging feature to provide topically relevant keywords to the image. It will increase the likelihood of people finding your images while searching or browsing.
6. Image originality - Popular or high-ranking photos tend to propagate throughout the internet. Stealing an image from another site is as easy as right-clicking and saving it. Use original photos where possible, even if you have manufacturer photos. Chances are, other people are using them as well. Experiment with watermarks or other ways of branding your photos to lower the probability of other sites using them.
7 . Save photos as .jpgs and graphical images as .gifs - Search engines will associate .jpg files with higher quality photographs, and .gif files with graphical content at 256 colors. Depending on the user query, the image search engine could favor one over the other.
Search engines are developing technologies to "see" an image and determine what the contents are. Google Images already allows users to filter photos based on whether or not a person's face shows up in the image. An image search for "paris" returns mostly photos of the Eiffel Tower and other landmark. Using the face filter, you'll get pictures of everybody's least favorite celebutante.
These image optimization tips will help you increase your site's visibility in the search engines and could help drive incremental traffic. Looking for more ways to dominate Google's Universal Search? Check out the other posts in the series below.
Updated list of categories covered:
7/31 - Google Maps
8/1 - Google News
8/2 - Youtube Video
8/3 - Google Images
8/6 - Google Blog Search
8/8 - Google Base
8/9 - Google Books
8/10 - Google Groups
8/13 - Google Code Search
Any others I'm missing? Leave a comment. Thanks!