I'm about to refactor some content on our site to be more search friendly and it occurred to me that most of my image file names are relatively short to reduce the size of the tags in HTML and I wondered if that was the best approach. As search engines give a great deal of weight to the URL of my documents, should I give the same consideration to the file names of my images? Does it matter if I'm not interested in the images being found - only the value they add to the search weight of the documents that link to them?
In general you need should name the files to describe what they are. Hopefully this will also align with your sites content. Then you should also be using alt tags to further describe what they are (which should still be inline with your sites content). This last tip is to help people with screen readers and those that need them...but this in the end will help spiders to sense that your site is what it says it is which will help you with your search rankings.
Oh yes! When doing an "image search", a search engine has less textual clues than when doing normal searches, so every one of the precious few textual clues that are available is going to be weighted more than it would for a normal search -- and that may well (and should) include the URLs used in <img src=
links to the image.
It has its importance but as most factors of on page optimization, any one element has a very limited effect. It's really the sum of all the elements you optimize that create a substantial impact on your rankings in the SERPs (Search Engine Result Pages).
So, yes, if you can have images with meaningful file names, it will help your pages rank better.