Alt text and image title text, their impact on SEO

SEO posting spring 2011Increasingly more and more of us are using CMS (content management systems) to upload new content to our sites.  This means we are constrained to use the fields provided by the CMS, but it also means it is easy for us to fill in all those little things we can often forget.  I mean alt text and image titles.

Alt text

The purpose of alt text is describe the image for visitors who are either visually impaired and cannot see images or visitors who choose to have images turned off.  They are therefore vitally important from an accessibility point of view.  It is alternative text for those who can’t see the image itself.

Who, you might say, would choose to view the page with images turned off?  Search engine spiders are the group we are interested in!  Spiders cannot see images so they read the alt text to understand what they are showing: alt text therefore is vital in optimising for image search, and  there is little doubt it plays a part in the main algorithm to determine web page rankings as well.  I think of SEO as gathering grains of sand with the bigger the pile the higher the page ranks.  Alt text may not be the biggest grain of sand, but they all help.

Alt text is what browsers show when you hover over the image.

Always use alt text to accurately describe the image.  Sometimes this can be difficult.  I use a little picture of a flower to illustrate these posts. I think it lightens up the page a bit and as I always use something in bloom from my garden, it helps to give a time context to the post.  I don’t want to confuse Google by have alt text saying ‘thrum eyed primrose’ in my alt text, so I use

search engine optimisation post spring 2011

which I believe is more useful to both any blind users who would surely ask why there is a picture of a primrose in a post about alt text, and also more helpful to Google.  My view here is that the spirit is more important the letter of the law.

Title text

The title attribute can be applied to any HTML tag, including the image tag.  Doing so creates a tooltip designed to appear when a mouse hovers over the content within the tag.  With images, the alt tag should (and usually does) take precedence.  The title tag should be used in the same way as a page title, to provide advisory information about the image and be written using the same guidelines, that is keyword rich, informative and with a maximum of 65 characters.

Image title text is nowhere near as important as alt text from an SEO perspective, it is a very small grain of sand.  But a grain of sand all the same.

Guidelines for optimising alt text and image title text

  • Keep them different, they do different jobs so need different text
  • Use keywords in both (as far as is appropriate), ideally this should be the page’s target keywords, or semantically related to them, but relevance is always key.
  • Best practice requires that every image should have alt text whereas title text is more optional.  The only exception is where images are used for non illustrative purposes.  Spacer gifs used to be a web page design tool, these are not seen by visitors and so should not have alt text.
  • Alt text – keep it short and keyword focused.  A few words should be enough.  Don’t forget the value of image optimisation, significant traffic can come from image search for some sites, and alt text is vital here.
  • Title text – include keywords but in a similar way to the page title, keyword rich, relevant, informative and interesting, and up to 65 characters in length.

As always, relevance is key.  Always work with your visitors in mind and do what will be most helpful for them.  That way you should also please Google who is, afterall, trying to do exactly the same thing.


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