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The Importance of Image Filenames – SEO Experiment

For those who follow my blog, you will probably know that from time to time I run some SEO experiments. This tries to find out the truth behind what really works to get better search results.

In my latest experiment, I have been running I looked at what elements on images have the biggest part to play in improving search rankings.

The three elements I looked at were:
  • Filename
  • Title Tag
  • Alt Tag

Image Filename

For most people when they upload an image to the website they leave the filename as it is,  such as DCMIMAGE10.jpg. However, it would be much better to name the file: Something-With-Keyword-In-It.jpg

Title Tag

The title is another one which gets forgotten quite a bit. Even website developers will leave off the title tag from code, only leaving the alt tag to describe the image.

All images in html should be constructed like - <img src="image.jpg" alt="image description" title="image tooltip"/>

Alt Tag

This is the one which gets talked about most in regards to image SEO. It means alternative text, as in display this as an alternative when the link is broken or when the image cannot load. It should be used as a substitute for what the image is.

That Is Best Practice

So that is best practice for image SEO. And Google outlines best practice in this post.

But what really works in the real world.

Experiment Time

So we thought we would do a little experiment.

Our hypothesis was that an image with the keyword in all three areas would rank the best. Our experiments included
  • no alt, title or filename
  • no alt, no title, But with a keyword in the filename
  • no alt, keyword in title and filename
  • no alt or file name but keyword in title
  • keyword in alt tag, but not in title or filename
  • keyword in alt and title tag, but not in filename
  • keyword in alt and filename but not in title

All pages contained the same Title, meta description, and content and included the same image (just with different tags).

I have been running the experiment for a couple of months now to see what results will come from it.

The Results

After the first couple of weeks, we saw a number of the pages get indexed.

Our control group was number 1 (so image had filename, title and alt tag containing keyword)
#2 – Just filename
#3 – Filename & Title
#4 – Just Alt Tag

After this, it seemed clear that Filename was a top factor, with the top three results all containing the filename.

I let the experiment run for a couple of months to see if we would get any changes on these results.
The top two spots bounced around between our control and just filename.

It now seems to have settled on the control group in number 1 spot. But this just goes to show the strength that naming all your image files with relevant keywords has.

Lessons

The lesson from this is, sometimes Google best practice is right (a lot of the time) and you should make sure you use all factors in your images. But the most important factor in SEO for images is the filename. If we just take a bit more time when uploading images and renaming them, we can help ourselves get better search rankings.

What should be my next experiment?

What should I test next? I want to hear from you. What should be my next SEO experiment? Let me know in the comments below.