Google Universal Search: Image Results Algorithm Decoded

By Janet Driscoll Miller | Jun 25, 2007
More Articles by Janet


During the past few weeks, the Search Mojo team has been working on deciphering the algorithm for Google’s new Universal Search results. Our first effort was to decode how image results are presented.

First let me acknowledge that not EVERY search produces image results. Different search query terms present different results — some with images, some without. We’re still investigating why this is true, but I do believe that some human intervention does occur at Google to determine which search queries will produce images and which will not. A few weeks ago, I wrote a post on Marketing Pilgrim about how a search for the term “Paris Hilton” did not yield image results, which I found surprising since that is one of the most searched items about the hotel heiress. Since that time, however, Google has now added images to this search query.

So what have we found so far?

Initial Results
Two of us at Search Mojo did preliminary searches on approximately 15-20 keywords apiece and compared several factors on each search. Some of the factors we examined were the appearance of the keyword in the following areas:

  • Image filename
  • Image alt tag
  • Page title tag
  • Page meta description
  • Page meta keywords
  • Page link text
  • Page alt tags (total)
  • Page content (all)
  • Page bold tags
  • Page H tags
  • PageRank of page

Consistently, we did see some factors appear to affect image ranking more often than others. Here are our two sets of results:


Image File
name

Image Alt Tag

Page Title

Page Meta Desc.

Page Meta Keywds

Page Link Text

Page Alt Tags

Page Content (Total)

Page Bold Tags

Page
H
Tags

Page
Rank of Page
84.21% 35.9% 36.8% 10.5% 15.8% 26.3% 26.4% 47.4% 26.3% 15.8% 15.8%
93% 53% 40% 20% 27% 27% 20% 60% 27% 7% 60%

We’ll continue to do phased testing on these elements, but these preliminary results show that the keyword appearing in the image filename and throughout the page content plays the most important role in ranking the image at the top of the image results in Universal Search Results. Additionally, by ranking these results, we can begin to determine the overall level of importance of each element:

Element Test 1 Test 2
Image Filename

1

1

Image Alt Tag

4

4

Page Title

3

5

Page Meta Description

6

7

Page Meta Keywords

5

6

Page Link Text

4

6

Page Alt Tags

4

7

Page Content (Total)

2

2

Page Bold Tags

4

6

Page H Tags

5

8

PageRank of Page

6

3

Interestingly, several elements had the same percentage of importance within a given test. In these cases, we ranked them as the same number in the table above. In BOTH TESTS, these elements seemed to weigh the same:

  • Page link text
  • Page bold text

PageRank of the page had varying results, and we do not believe it is a major part of the image result algorithm.

We’ll perform this same test several more times to compare our results. But for now, I think it’s safe to assume that pages with images should contain the keyword throughout the page content and in the page filename to improve the likelihood of high image ranking in Universal Search results.

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  • http://qwertysqoncepts.blogspot.com/ qwerty

    My tests weren’t as extensive as yours, but they pretty consistently indicated that the image’s file name wasn’t particularly important. It really came down to the same factors of the page that make it rank for the keywords: keywords in the content and the title, with some indication that keyword proximity to the image my help.

  • http://qwertysqoncepts.blogspot.com/ qwerty

    My testing wasn’t as extensive as yours, but I’m not seeing much importance for the image file name at all. It seems to me that the factors that help an image to rank for a given keyword phrase are for the most part the factors that help the page that contains that image to rank for the phrase.

    See http://www.qwertysqoncepts.blogspot.com/2007/06/image-optimization.html