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10 factors affecting your Image search ranking

Is having your keywords in your image ALT tags on your images enough to rank high on Google Image Search?

The answer is NO! This post attempts to further your understanding of how Google ranks images.

This is important for certain types of business, apart from the fact that it is a good source of traffic for your website.

I bet you thought that all you need to do is ensure you have your main keywords in your ALT tags? Well think again!

There is a host of other factors which determine how high your images rank, and based on my research, the ALT tag is one of the LEAST important.

I’ve just done a few hours of research to try and understand the importance given to each of the ranking factors, i.e. which have most effect and which have least effect on the ranking. What I did was compare the following factors…
Factors affecting your image search ranking

  1. Image ALT tag text
  2. Image Title Tag
  3. Search Text in filename of images
  4. Search Text in URL of page containing the image
  5. PageRank of page containing the image
  6. Search text in TITLE tag of the page
  7. Proximity of search text before the image (in the HTML)
  8. Proximity of search text after the image (in the HTML)
  9. Search Text in a H1, H2, H3, or H4 tag

I analysed 2 different search terms (“bespoke sofa” and “tyrannosaurus”) and got similar results for both. However as only 2 search terms were analysed, you would probably want to try the same with a few of your own keywords.

I also analysed the first page of image results (top 20), but I could see a pattern emerging even with this small number of results.

In summary, what I found was that the Proximity of search text to the image is THE most important factor, followed by whether this search text is in a heading tag or not and then the Google PageRank of the page containing the image.

RESEARCH RESULTS ON IMAGE RANKING

Here are my findings in more detail going from Most important to Least.

1. Proximity of Search text to images – Basically this is the most important factor. It did not seem to matter whether the words came before or after the image, but the closer, the better.
Example….
Some words here + SEARCH WORD + IMAGE + Some more words here
..ranks better than…
SEARCH WORD + Some words here + IMAGE + Some more words here

2. In 39 out of 40 images, (both tests) the search term appeared within 50 words of the image.
These findings are borne out by a post on Trafficlicious.com

3. Whether the search text is in a heading tag or not – There is a higher ranking when the search text close to the image is in a H1, H2, H3, or H4 tag.

4. The Google PageRank of the page containing the images – Apart from proximity to the image, the PageRank seems to be the strongest factor especially for less competitive search terms. For example I searched the term “bespoke sofa” and the page with the #1 ranking image had the highest pagerank – even though the words close to the image were “designer sofa” rather than “bespoke sofa”. This suggests that LSI (latent semantic indexing) is also used for images. The words associated with bespoke sofa were “designer”, “furniture”, “upholstery”, “made to order”.

5. TITLE tag of page containing the image – Having the search text (or related LSI term) in the TITLE tag of the page has an important influence. For “Tyrannosaurus” it appeared in the TITLE of all top 20 results. But it is not the most imporant factor. In the other example the search term “bespoke” or “sofa” appeared in the TITLE of only half of the pages.

6. Focus of the webpage – I subjectively looked at how focused each page was visually for each search term. In general, the more focused the page (less images and text about other topics) the higher the ranking – of course there were a few exceptions.

7. Keyword in Page URL – Having the search text in the URL of the page containing the image might help but for bespoke sofas, there were top ranking images which did not include the search text in the url.

8. Search text in the Image File Name – As above, this did not seem to have much effect. However if all other factors were equal between two pages, the file names would probably have an influence.

9. Image ALT text – Despite all the focus by SEO experts on ensuring you have ALT text tags on all your images, ALT texts were missing on 13 out of 40 of the results. There is more information about optimizing the ALT tags on images on this post.

10. Image TITLE attributes – These did not seem to make any difference and were missing in most of the results.

SEO by the sea has some more interesting information on getting ranked in Image search.

My conclusion from this limited research is that the single most important factor to have your images ranked well is to ensure your search text is within a few words of your image, and if possible inside a heading tag. Also the more focused your page is about the search term, the better the chance the image will rank high. You can’t really do much about your PageRank but there were PR0 sites ranking for both terms.

Please feel free to comment or add your findings below….

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