Image optimization is similar to the SEO we do for normal web page optimization, but slightly different. The idea behind image optimization is that you’re trying to get your image to rank in Google’s image search. And remember that image search blocks are sometimes pulled into Google’s regular (universal) search results:
At one point image search was a significant part of the SEO strategy for certain kinds of sites. They collected (or stole) great images on topics that people were interested in, and worked to get those images to rank well for related searches in Google’s image search. The user would see the thumbnail and click through to the site to get access to the full-sized image.
These sites typically monetized their sites with ads, so every time someone clicked through to get to the full-sized image, they landed on a page that had some ads as well as the image they were looking for. Some ecommerce sites even got a decent amount of traffic from image search: image traffic converted worse than regular search traffic, but it still converted, so they tried to get their product images to rank.
Google Takes Your Images, and Your Traffic Too
Unfortunately, Google has since changed image search as part of its efforts to keep people from leaving Google. Now in Google’s image search you can click on any image to see a larger version right in the image search results, and Google gives you the option to click through to the site, or the option to just view (or download) the full-sized image directly from Google.
When they launched this feature, traffic from Google image search dropped dramatically. Image search was never a primary focus of SEO, but its value is vastly lower than ever now that Google just takes your images and serves them to users themselves.
That said, you can still get some traffic through image search. Let’s talk about what you can do to optimize your images for that small percentage of image traffic that still remains to us. It’s not hard to do, so you may as well optimize for it all. Just don’t sink a huge amount of time into it.
Image SEO Ranking Factors:
- The filename of your image should include the keyword you want to rank for. Don’t name your image “DCM8873.jpg” — name it “cute-cat-slays-dragon.jpg” This is a substantial ranking factor in image search.
- The image alt text helps Google understand what your image is about. This text appears within the image html tag like this: <img src=”blah.jpg” alt=”Cute kitten slays real life dragon!”> Obviously your alt text should also accurately describe your image, and be pretty short.
- Surrounding text: a meaningful image ranking factor is the text on the page that the image lives on, especially the text immediately before and after the image. Google assumes that your image will be relevant to the part of the page where you insert it.
- Links: images can have authority just like web pages do. The more people that link to a picture, and to the page that the picture is on, or who embed your picture in their sites, the better that picture will rank.
- Size: Google seems to prefer delivering larger images over smaller ones, though other ranking signals can certainly push the smaller images to the top.
It’s pretty easy to be in the habit of saving your image file name with logical keywords, and likewise it’s easy to toss in some decent alt text when you’re embedding the image in your content. You should be optimizing the text on the page itself anyway, so all in all tending to some basic image optimization isn’t really much additional work.
If image search is an important part of your strategy, it may be worth your while to create an image XML sitemap. Similar to a regular XML sitemap, the idea behind the image sitemap is to help Google find all the images on your site so that it can include them in its image search. Of course just like a regular sitemap, the presence of an image sitemap does not in any way guarantee that Google will choose to include your image.
However, unlike regular sitemaps the image sitemap can actually help your rankings: because Google doesn’t understand images very well, the information about the image that you include in the sitemap can help Google understand the topical relevance of the image, which can help it rank better.
You can learn how to create an image sitemap here.