Optimise for Google Image Search

May 29, 2006

Google Image search operates a little differently to the main search, and therefore when you optimise for Google image search, there are a few extra things to keep in mind. This article summarises the main things to note when optimising for Google image search. Yahoo and MSN also have an Image search facility, and most of these points also apply to Yahoo and MSN.

What is Google Image Search?

People looking for images will use Google's image search facility instead of the main search. This makes sense when you are looking for stock images or want to see more about a topic.

The Google Image bot

Google has a bot which spiders the web for content, which it then includes in the index. For image results, Google uses a different bot, which indexes only image results. The key difference between the two is that the image bot visits much less frequently. While Googlebot may visit every week, Googlebot-image may only visit your site every 6 months. Getting images indexed is a very slow process.
All the more reason to get started early.

Google is a blind user

The W3C keep talking about how you should design your website for blind people, who use screenreaders to browse the web. While many web designers ignore this because it's such a small portion of the market, keep in mind that Google is also a blind user.
Because Google can't actually see your images, it relies heavily on how you describe your image.

The Google Image Search Algorithm

I won't pretend to know how the Google Image search works. But if I was writing one, I would start with the following ...

• Use image ALT tag to determine content
• Use image Filename to determine content
• Use surrounding text to determine content
• Use overall page theme to determine content

In lieu of any further instruction or in-depth analysis, this is a logical place to start.

ALT Tags

Alt tag spam has been around since the dawn of time. Because it works. I'm not going to advocate spam, because although it may work in the short term, it's longevity that decent websites want.
The best thing to do with an ALT tag is to describe the image - as you would to someone over the telephone.
If your image is a picture of a bamboo coffee table, then your Alt tag should start with "Bamboo coffee table". To optimise a little further without being accused of spamming, you can expand this to "Bamboo coffee table from Bambusero, Auckland NZ".

Image Filename

I made some recommendations to a friend this morning on how he should name his images. I think the examples I gave sum it up nicely.
Osiris009.JPG should be osiris-coffee-table-9.jpg
shelvesdetail2.jpg should be bamboo-rimu-bookshelf-2.jpg
0763_sam.jpg should be bamboo-flagpole-763.jpg
0764_sam.jpg should be bamboo-lengths-on-trailer.jpg

The filename should describe the content of the image. The best way to describe an image is to use relevant keywords, and this is also the best way to describe the image to Google, Yahoo and MSN. By naming your images to logical user friendly names, you are also performing SEO on your images.

Optimised Image example - Sunset on the Hokianga Harbour

The above image was taken on the Hokianga Harbour, Northland New Zealand on a fishing trip in Feb 2006. In 6 months time, this image has every chance of ranking well for "hokianga harbour sunset" and with enough pagerank and incoming links, it can rank highly for "hokianga harbour" as well. Photo by Alexander Burkhardt.

Surrounding Text

Once again, what appears to be SEO is actually a usability rule. The Alt tag describes an image for those who can't see it, but I like to use captions on images as well for those who can. An alt tag may describe that an image is taken in Africa - the image looks like a beautiful scene somewhere, but it could be anywhere. For those who can see the image, reinforce it's meaning by adding a short caption underneath. Or make sure the surrounding paragraph explains what the image is.

Overall Page Theme

Place some Google adsense ads on your page, and see what content Google chooses for your ads. Are the ads related to the content? Do they include (roughly) the search phrase you are targeting. If not, Google may be having trouble deciding what your page is about. A clearly defined page topic is likely to improve rankings for both text and image search.

Technical Considerations

Here are a few things to watch for.

• Don't optimise template images or backgrounds for your page. Nobody wants to find your menu background when they are searching for real image content. Use alt="" on these images, and don't load keywords into the filenames. My menu backgrounds are often named "bg-menu.gif" or similar.
• Google will only index files that look like images. If you use scripts to generate dynamic images, do some research into caching or rewriting instead. As far as the Google Image bot is concerned, "image.php?file=example.jpg" is a php file, not a jpeg.
• Decide on a logical folder structure for images and don't change it. Getting images indexed is hard enough and slow enough, so don't delete all your hard work by renaming or moving an image 6 months after uploading it.

Conclusions

Once again, optimising images comes down to good web design practice, and good housekeeping. Do this consistently and from the start, and getting your images appearing in the SERPs will come naturally.

Tags: googlebot images seo googlebot images seo