Proper use of image title and alt tags will contribute to a better user experience as well as greater odds of your site's content coming up in image search results.
Additional actions you may take to optimize your images for search include giving images descriptive file names, offering helpful contextual information in captions and surrounding content, giving others the ability to use your images elsewhere so long as they link back to your site, and providing images of excellent quality.
What Are Image Title Tags?
Title tags enable one to attach words to an image that will appear as a tooltip when a visitor hovers his or her cursor over it (tooltips are those snippets of text you sometimes see when you hover your cursor over an image, a link, or some sort of functional element). Title tags are generally succinct and descriptive.
What Are Image Alt Tags?
An alt tag is a word or series of words attached to an image that displays when an image does not properly load. The text presented within an alt tag might also:
- Appear when a cursor hovers over an image (only in some browsers; usually the title tag is used for this purpose)
- Be utilized by visually-impaired people visiting your page (screen readers are trained to pick up image alt tags)
Are Image and Alt Tags Visible?
Title and alt tags are one of many HTML elements of a page; neither the words in these tags, nor elements the code itself, are typically visible to people viewing a page through a typical browser (unless one hovers one's cursor over an image or an image does not load).
Should you like to see image alt tags as they would be shown when an image does not load on your site, visit your site using a text-only browser, such as Lynx.
How to Add an Alt Tag and Title Tag
If you are using some sort of CMS to upload and display images online, you will probably be given the option to add a title and alt text through a text box. Some sites and platforms limit the amount of information you can add to an image or do not specify which fields are applied to certain tags. To ensure your descriptions are appropriate even if you are not sure where they will be used, try to be as succinct and descriptive as possible when entering this information.
Should you be building your own page from the ground up, here is an example of how title and alt tags will appear within the context of an image: <img src="bowlofchili.gif" title="bowl of chili" alt="a steaming bowl of chili">
How to Describe Images in Title Tags and Alt Tags
For title and alt tags, we recommend giving your images short, clear descriptions (under 20 words), such as "a fluffy white kitten," "an 18th century diamond tiara and scepter," "President Clinton addressing an audience of retired entrepreneurs," or "boating accident."
We do not recommend utilizing:
- More than 20 words
- Spelling mistakes
- Random words
- Non-descriptive terms
- Long lists of keywords (this will hurt you, not help you)
Why Descriptive Tags Matter
It is important that your alt tags are descriptive for several reasons:
- Should an image not load, it is important that visitors know what they were supposed to be shown
- Image search engines depend on consistent descriptions when choosing what will rank well in image search results
- Spammy alt tags (i.e. those comprised of long lists of keywords: kitten, cute kitten, fluffy kitten, adorable kitten, etc.) can actually hurt your prospects with search engines (not to mention a visitor's perception of your authenticity)
Additional Tips for Creating Search-Friendly Images
- Give your image files descriptive names: For example, you might change the file name of an image of a ballet dancer from DC10333020.jpg to Ballet-Dancer.jpg.
- Give your images descriptive captions: Captions are just another way to add context and additional information to an image; make use of them when appropriate.
- Make sure the subject matter of an image matches with the subject matter of the page: While image search engines utilize image tags and file names when deciding how to prioritize content, they also draw information from the page on which images are displayed. If that page displays information that strengthens the theme of your image (e.g. a page about grilled cheese sandwiches containing a well-tagged picture is of a grilled cheese sandwich will have better prospects of ranking well in image search than a page on SEO that contains a well-tagged picture of a grilled cheese sandwich).
- Give your image a Creative Commons license: A Creative Commons license enables others to use your original images elsewhere online provided that they attribute and link back to you. Giving images Creative Commons licenses is therefore an excellent way to get people to link and drive traffic to your site. We created a dedicated guide to applying Creative Commons licenses to your images should you be interested in learning more.
- Provide high quality, original images: The more crisp, clear, alluring, and attractive your images are, the better- not just for search engine optimization, but also for social media-friendliness, increasing one's odds of having a Creative Commons-licensed image used, and giving visitors the best experience possible.
Want more advice? Let Google's Matt Cutts and Peter Linsley walk you through the basics in the videos below, and read through Google Webmaster Tools' image publishing guidelines.