Jakob Nielsen's Alertbox for January 11, 1998:

Using Link Titles to Help Users Predict Where They Are Going

One of the greatest problems on the Web is that users don't know where they are going when they follow hypertext links. Some Web browsers have recently added the ability to pop up a short explanation of a link before the user selects it. Such explanations can give users a preview of where the link will lead and improve their navigation:

bad links are less likely to be followed; users will waste less time going down the garden path
increasing users' understanding of good links helps them interpret the destination page upon arrival: disorientation is reduced

The link explanation is called a link title and is very easy to encode. For example, the HTML code for making my name (immediately above the headline) into an anchor is <A HREF="http://www.useit.com/jakob/" TITLE="Author biography">. If you rest your cursor on my name, the words "Author biography" will pop up after about a second if you have a browser that supports link titles (most don't).

Having the title "Author biography" pop up when the user is thinking about what might be linked from my name gives the user an indication of the type of information he or she can expected to get from following the link. Among other things, it makes it clear that the link is not a "mailto" link that will spawn an email message.

Guidelines For Link Titles

The goal of the link title is to help users predict what will happen if they follow a link.
Appropriate information to include in a link title can be:
- name of the site the link will lead to (if different from the current site)
- name of the subsite the link will lead to (if staying within the current site but moving to a different part of the site)
- added details about the kind of information to be found on the destination page and how it relates to the anchor text and to the context of the current page
- warnings about possible problems at the other end of the link (for example, "user registration required" when linking to The New York Times)
Link titles should be less than 80 characters, and should only rarely go above 60 characters. Shorter link titles are better.
Do not add link titles to all links: if it is obvious from the link anchor and its surrounding context where the link will lead, then a link title will reduce usability by being one more thing users have to look at. A link title may be superfluous if it simply repeats the same text as is already shown in the anchor.
Do not assume that the link title will look the same for all users. Indeed, auditory browsers will read the text aloud and not display it visually. Different browsers will display link titles in very different ways, as shown in the figure.

Same link title shown in Windows'95 and on a Macintosh

Finally, note that link titles do not eliminate the need to make the link anchor and its surrounding text understandable without seeing the link title. Users should not have to point to a link to understand what it means: the link title should be reserved for supplementary information. Also, for many years to come, some users will have browsers that do not display link titles.

Early Adoption of Link Titles Recommended

Normally, I advise against using new Web technologies for the first year after they have been introduced. In most cases, using anything new is asking for trouble and will alienate users with older browsers.

Link titles are an exception to the need to wait a year. First, their use does not hurt users with browsers that don't display link titles (assuming you follow the guideline to keep the link anchor understandable when the link title is not displayed). Second, a browser that does not understand link titles will simply skip them. Since the title is not a new tag or otherwise intended to influence the layout of the page, the page will look exactly the same whether or not the browser does anything with the link titles. The only downside is that link titles will add approximately 0.1 seconds to the download time for a typical Web page over a modem connection. This is a rather harsh penalty, but worth paying because of the increased navigation usability for those users who do get to see the link titles.

At the time of this writing, link titles will probably only be seen by 25% of the users. Normally, this would be insufficient to employ a new Web technology, but since link titles are extremely easy to add to your pages and since they do not pose any danger to users with older browsers, it makes sense to go ahead and start using link titles. Link titles are one of the first enhancements to the Web that actually help people navigate (as opposed to simply making pages look more fancy). Since we know that users have horrible problems finding things on the Web, we should give them all the help we can.

January 25: The case for micropayments

See Also: List of other Alertbox columns