If your business has a CMS that's managed in house or you've been knocking around in Digital Marketing for a while, you will almost certainly have heard this question before. If it's you that's asking said question, you, my pedigree chum, are in luck. That's what this blog is all about :P
Not to be confused with the image file name, Alt text is the HTML attribute given to an image to help provide an accurate description of what's in that particular image.
For SEO purposes it needs to ideally contain a relevant search term (do not just spam keywords... it's 2016 ffs there's no place for dat black hat shiz no more).
More importantly, from an accesibility point of view it needs to actually be an accurate description of the image. For best results try to organically blend the two approaches comme ça -
Hover over the image above with your mouse > right click > then hit "Inspect" or "Inspect Element"
You'll be confronted by this particular line of HTML:
<img src="//cdn2.hubspot.net/hub/1759064/hubfs/Josh_Delivering_Local_And_Mobile_SEO_Training.jpg?t=1468925170820&width=713" alt="Josh Delivering Local And Mobile SEO Training" width="713" title="Josh Delivering Local And Mobile SEO Training" caption="false" data-constrained="true" style="width: 713px;">
You can see the alt text in purple. It describes the image clearly and contains a search term for one of our services - Local And Mobile SEO Training. If you can't justifiably or organically inlcude a search term, just make sure your alt text provides an accurate description for accesibilty purposes.
N.B. also notice that i've used the same alt text description for my file name (.jpg), always rename your image before uploading, don't just leave it as DSC08501.jpg or pic_2.png
But until that time when Google becomes self aware and destroys all human life, we have to help spoonfeed and highlight information as much as possible. By attributing an image with an alt tag you're adding more crawlable text to your page content that Google can read and utilise for indexing.
We've seen a quite a few cases over the years where businesses have seen a marked boost in rankings just by adding alt text to their images! Not only will you perform better in standard SERPs, the images that you add alt text too will start to appear in Google Image search results. Top stuff!
Likewise the same alt text can be viewed and read in a similar manner by screen readers, software typically used by those with impaired vision that converts web pages to speech.
The web should be accessible to everyone so if you take anything from this blog at all, please add alt text to your images and improve your sites accessibility. Google will love you for it and you'll help make the internet a better place!