Optimising images for keywords and phrases is an important aspect of onsite SEO for anyone wishing to get better search results and more traffic to their web pages. Search engines like Google or Bing cannot easily take an image and understand its meaning though they are getting exceedingly better at it with modern artificial intelligence.

Firstly we’ll discuss why you need to optimise your images on your web site and then how to go about it.

So Why Should You Optimise Images For Search Engines?

As mentioned above search engines cannot understand an image very well. It takes a lot of computing time to process an image so is not currently feasible. Search engines therefore extrapolate the data contained around the images in the form of text.

How to Optimise Images

The most important areas around the image that search engines look for clues as to what the image is are:

  • The text immediately preceding the image is of importance
  • The text immediately after the image
  • The alt attribute directly describes the image
  • The file name of the image is a strong signal to search engines

Also to be taken into consideration is:

  • The position of the image on the page
  • Image data size – this effects page load time and this is a ranking factor
  • Including Images in XML Sitemap Files

Immediate On-page Text – Preceding And After

The text immediately before and after the image are pretty self explanatory. You could add keywords in a small paragraph before an image and perhaps a caption below for example, optimising for the key phrase ‘curly brown hair’:

Notice how synonyms are used and not overly. Locks are a synonym of hair particularly when it’s as curly as this gentleman’s!

Alt Text Attribute Optimisation for Images

As for the alt text; the alt is a HTML image attribute and is an abbreviation of alternative. It is used to put descriptive text about an image for text based browsers that don’t render pictures. Its HTML code looks like this using the same example as above, please note the file name (src=):

Optimising images with alt text.

Search engines also use this as a strong signal to what an image is about. In fact, Matt Cutts, Head Programmer from Google’s web spam team says (in more or less words): websites with little textual content but with lots of pictures are to make sure that the alt tag is used accordingly to accurately describe the image.

Think around an upper limit of 16 words before Google stops reading image alt text.

On-page location – above the fold or below?

Also important according to Matt Cutts is image placement. Alt text from an image placed at the top of your page is more important in Google’s point of view and probably in Bing’s too. For example the image of the smiley man with curly brown hair above would rank higher in the search results for its alt text keywords when placed above the fold of the web page (top of the monitor) and not in the bottom.

Optimising Filenames For Images

In the above picture please note the filename; this is a dead give away to search engine image searches what your picture is about and in this case we’re optimising for the key phrase ‘curly brown hair’.

Image Size as a Ranking Factor in The SERPs

Don’t forget to save images in a compressed format such as gif or jpeg. The load time of a website is taken into consideration by Google & Bing and there is a correlation between page load times and ranking higher in the search engine result pages.

Save the image at a suitable image size too so if you need the image on your copy page to be 400 pixels by 500 pixels then save it as this size in your choice of image manipulation software.

This drags-up another point: if it’s your job to develop the webpage make sure you apply the CSS width and height styles so the page loads neatly and timely. A webpage will not load content past an image until the image is loaded unless the width and height values for the image are set.

We hope you enjoyed reading our document on SEO for optimising text for images and image search.
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