Hacking Images for SEO Purposes
Posted by drew on Oct. 12, 2014, 6 p.m.
More and more these days, webmasters are realizing that quality content is the key to SEO. It takes times and effort to produce, but useful, quality content can set you apart from your competitors.
However, there are still some things about SEO that are more technical. Using the images on your site effectively can help your pages rank for your target keywords. This post functions as a quick guide to the different things you should do with your images in order to get the most SEO benefit from them.
Image Alt Tags
Image alt text refers to alternate text that will be displayed in place of the image, should the browser not be able to display the image, or should the user choose to block all images. The alt text is also used by search engines to understand what the image contains, since search engine spiders cannot “see” what is in the image.
For example, the HTML for an image with alt text would look something like this:
<img src=”/example_image.jpg” alt=”Optimized Alt Text”>
When a search engine looks at your alt text to understand your images, you have the opportunity to include SEO keywords, telling the search engine what the image contains, and what the page is about in general.
A perfect example of this is on e-commerce sites, where most pages will have product images and will be trying to rank for the name of the product. Let’s look at an image tag on this Amazon page for a Nikon D7100 Camera:
<img alt="Nikon D7100 24.1 MP DX-Format CMOS Digital SLR (Body Only)" src="http://ecx.images-amazon.com/images/I/91Ns138GTAL._SX522_.jpg">
The source (src) of the image shows where the file is kept, and the alt text includes a description of the image and the keyword phrase they are trying to rank for.
Pro Tip: The name of the image file in that last example is 91Ns138GTAL._SX522_.jpg, which doesn’t have any keywords in it (unless that string of numbers and letters is meaningful to you). You can double down on your SEO optimization if you include descriptive keywords in the image file name as well.
When two sites are closely competitive in the search results, Google uses the site load speed as a factor to determine which site should rank higher.
Because of this, your image file size is an important consideration. Large images can take much longer to load on your website than smaller images, so it is best to keep image sizes as small as possible (without sacrificing the quality of the image).
It is also important not to simply have the browser resize the image to make it smaller. This will force the larger image to load first, and then be resized, so you won’t actually make your page faster by doing this.
Just how a sitemap.xml file can be submitted to help Google find and index your pages, you can use an image sitemap to help Google find and index the images on your site, so they can be included in Google Image Searches.
You can either create a separate image sitemap or include image tags in your existing xml sitemap. Image tags on an existing URL in an xml sitemap look like this:
You can list up to 1,000 images on each URL in your sitemap. For more information on using image sitemaps, check out this how-to from Google. This article explains all the different tags you can include in an image sitemap to describe the image.
Structured data refers to HTML tags that tell search engines about the information on your page. It is important to distinguish between telling a search engine information (a series of words and numbers) and telling the search about that information (for example, maybe those words are names, and the numbers are addresses, ages, phone numbers, etc.)
Including structured data through your entire site is always advisable, as it helps search engines better understand what your site is about. Images are no exception to this rule.
Your options for structured data are microdata, microformats, and RDFa. It’s generally advised that schema.org microdata is the preffered method. You can learn more about implementing structured data on images here.