I want to implement tooltips on product screens in a web application for Telecom. What should be the maximum tooltip text length?
The short answer: as few as possible and still communicating the message in a meaningful way.
The long answer: The reason to display a tooltip message varies a lot. But from a User Experience point of view a tooltip can’t be the only way to inform a user. There are users that don’t understand that there is a tooltip to begin with and much less understand how it works. I’ve seen users who get frustrated in test where the tooltip was the only communication way – and the task where not completed because of that. But you can use the tooltip as a reminder for those users who know what it is and how to activate them.
The point of the tooltip is to communicate a message. The more effective the message, the better it is. Maybe you should ask yourself what we are trying to communicate here, instead of the number of characters we could squeeze into the tooltip box.
As an example – imagine the second password textbox label in a registration form. The tooltip could say “You need to fill the second password textbox in the exact same way as the first one in order to complete your registration”, which would be hard to read if you knew the tooltip would disappear in X seconds. Instead the tooltip could say “Retype your password”. Then you’ve communicated the same message more effectively in fewer words and in a more useful way.
The time the tooltip should be visible depends on how your intended audience is able to get the message communicated by the tooltip.