Posted by Sam Battin, Senior Natural Search Specialist Understanding how robots think is a good way to predict how your actions will affect your site. Remember, robots are stupid. They’re great at doing what they’re told, but if they’re not told to do something, then they’ll never do it, as we’ll soon see… A picture is worth a little more than 990 words, but on a Web page, a picture might not be worth anything to a search engine robot. If your Web page contains images that you think people will search for, this article will help you understand how search robots “think” about images, and give you some pointers on what you should do to help search robots understand your page better. Back in the early days of the Web (that is, “The Web” and not “”), search robots were designed to read text only, as we see in this Google result from 1999. You’ll notice there is no “Images” link anywhere on the page:

Think Like a Robot - Images 1

Google didn’t offer image search until 2001, and originally presented visitors with tiny index of only 250 million images (by 2010, Google had an index of ten billion images). Though Moore’s law has gone through eight iterations since the introduction of image search, the search engine robots indexing your site still aren’t much smarter than they were back when the 1.3 GHz Pentium 4 processor was state of the art. To a search engine robot reading a Web page, your image does not appear as the visual representation of an object.  Instead, search engines “see” your image as a line of code that references a particular file somewhere else on the internet. For example, if your image is a JPG file named “image”, then the following table shows you how much search engines know about your picture vs. what you can see:

What human visitors see

What search engines see

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<img src=”image.jpg”>

Search engines are designed to read text. Text is more important than images because that’s what people use in their search engine queries. To put it another way, people don’t use images to make search queries. Currently, you have to type “Mona Lisa” into Google to see images related to this query, and there’s no way to give Google a “Mona Lisa” picture and have it know what you mean (at least, not yet…)

Though search engines are looking for text when they crawl your page, they know that images are important too. If a search engine isn’t told anything else about your images, the following is most of the information search engines can index in your image:

  • The number of kilobytes
  • The file type (JPG, PNG, GIF, etc)
  • The number of pixels wide by pixels tall

By this definition, the Mona Lisa is about the same to a search engine as Hello Kitty. To get visibility in image searches, you have to give search engines help by telling them about your pictures with additional text.

To improve image visibility on search engines, you will need to surround your images with descriptive text that matches the words your visitors will type in a query. This will help search engines understand what’s inside an image file, even if they can’t “see” an image like we do. The table below shows a number of different places on and off your Web page where you can add information that explains image contents:

Differentiate with:

“Hello Kitty”

credit: Jose

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“Mona Lisa”

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File Names



File Directory Locations



Image ALT attributes

ALT=”Hello Kitty”

ALT=”Mona Lisa”

Image Captions

Hello Kitty cosplay.

Mona Lisa painting in black and white.

Text paragraphs near the image

Hello Kitty first appeared in 1974 Japan under the name “Kiti Howaito”…

The Mona Lisa is a painting from the early 16th century, and thought to be a portrait of the wife of an Italian nobleman…

Anchor text of links pointing to the page where the image is

Famous Cats

Davinci Paintings

This level of detail provides search engines with textual information about your image that they can use to connect your site’s content with relevant search queries. 

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