Images are important to websites. They add value to the design, break up the text, and help communicate a message. In terms of SEO, the code used to add an image provides you with an additional optimization opportunity. It’s called the ALT tag, or alternative text, and when used correctly can give your site an advantage.
What is an ALT Tag?
Search engine spiders can’t read the text in images. To understand what an image is about, it relies on ALT tags, the image file name, and text around the image. The ALT tag is an attribute that allows you to add descriptive text that can be crawled by search engines. In fact, if you don’t currently use ALT tags and don’t disallow images in your robots.txt, do a search for your URL at Google Images and see which words Google associates with your images. Most web design software allows you to add an ALT tag, or you can place it directly into the HTML. Here is an example of HTML with the image and ALT tag.
The Purpose of ALT Tags
The purpose of the ALT tag is to describe the image. ALT text appears when the image is loading, when a person disables images in a browser or mobile device, or they use screen readers and text browsers. In these instances, the ALT tag, or image description, would appear in place of the image or be read by a screen reader. IE browsers will also see the ALT tag when they run a cursor over the image, provided the title tag is not also used.
Importance of ALT Tags
In terms of SEO, the importance of the ALT tag lies in its ability to help boost your web page rank and if you choose to have images indexed, increase your exposure through image search. I don’t recommend allowing your images into the index; however, some Webmasters prefer this. In those instances, let’s say you sell blue widgets on your site, but don’t use the ALT tag. Search engine crawlers won’t know what your image is about and your images will not appear in image searches. If used well, and not abused, the ALT tag can help improve your rank and better index your images for image search if you choose to do so.
Optimizing ALT Tags
Try to be brief, clear, and contextual when using these tags. You want to describe a particular image in just a few words, but with keywords that will help rank. Check out the top 10 sites in Google for the keywords your page targets and see how they’re using ALT tags. Never keyword stuff (spam) the ALT tags–not even if your competitors are! This will hurt, not help, your site. You also want to use relevant words, but mix it up, don’t use the same phrase each time.
Here are some examples of ALT tags:
Blank: Not Optimized:
<img src="Chicago.jpg" alt=""/>
Vague:
<img src="Chicago.jpg" alt="Chicago"/>
Relevant:
<img src="Chicago.jpg" alt="Site of Fort Dearborn in Chicago">
Spam:
<img src="Chicago.jpg" alt="Chicago Illinois fort dearborn history Chicago archaeology history sites pizza Cubs Sox Black Hawks Chicago Illinois tours sightseeing guided tours"/>
In the video below, Matt Cutts shows you what makes a good ALT tag.
[youtube]http://www.youtube.com/watch?v=3NbuDpB_BTc&feature=player_embedded[/youtube]
Don’t Abuse ALT Tags
First and foremost, some web users rely on screen readers to access sites. If your ALT tags are stuffed with keywords, they have to listen to all of that, which is rude. You want to use and optimize the ALT tags, but also be mindful of who really relies on them. Secondly, Google uses freelancers to personally check out sites. If one sees you’re spamming ALT tags that could hurt your rank. More likely than a visit from Google quality control, is a spam report submitted by one of your competitors!
ALT tags are now a basic requirement for your site. If you’re not using them, go through your code and start adding them today!
Jimvesting says
Definitely important to use Alt tags, it’s amazing how many hits I get from Google Images… and I know that all the work I put in to categorize all of my images is going to boost my SEO. Great post, very important stuff
Brock O'Leary says
Perhaps my memory is failing me but I recall JW always recommending that we disallow the crawling of our images (contrary to what someone like Howie Schwartz would recommend) because the spiders often have issues with them and the traffic from Google images is useless traffic because it rarely converts. Did something change?
Chel says
Can you apply alt tags to Flash in a website as well?
paul says
if site do not use the alt tag in image then can be cause of site violation in google search??
Jerry West says
Not using the ALT tag will NOT be a site violation by Google. Personally, I don’t allow my images to be indexed on my sites as most traffic from Google Images are from those looking to hijack images for their own site design or looking for free porn.