Your product is useless if no one can use it.  But how do you know how usable it is?  You can try it yourself, but you are not the user. (“You are not the user” is practically a mantra here at HCII.)  One set of methods, usability inspection, provides a framework to systematically evaluate a system yourself or with the help of others versed in the methods.  But really, you want to know how actual users experience the system.

Usability testing is a systematic way to see how real users get along with your design.  There is much literature around usability testing, which you may want to read.  Or you can just dive in using some of the easy tools that are available these days.

If you have access to users and can put them in front of your computer, there is software that can record both the screen and a webcam at the same time so that you can go back later to watch and listen to the user while they’re using your software. The best is Silverback, which is pretty slick but only for Mac.  (For Windows, keep looking.)   Because it’s recorded, you can skip over boring stuff and replay interesting stuff over and over.  You don’t even need to be there to record it, if other people are helping you.

Then there’s remote testing. If you’re testing a web application, your users don’t even have to leave their computer.  Today I came across these remote testing services and they’re pretty great:

• Low cost usability testing – UserTesting.com
• userfly — Web usability testing made easy
• Chalkmark – User Interface Testing

userfly is impressive and also the cheapest.  You add a Javascript string to your page and the everything the user does on the page is recorded.  Then they play it back for you, showing the mouse move around, clicks and keypresses.  It has some difficulties updating with results of AJAX calls, but they’re working on that.  They offer 10 recordings per month free, so it’s worth trying.

UserTesting.com is like a mix of Silverback and userfly.  For $29, they provide the user for you and record a video of their screen, with an audio track of them thinking aloud using your website.  Apparently the user also provides a written summary of the problems they found.  I haven’t tried it since it costs money, but I wonder who the users are.  I expect they’re experienced evaluators, which helps in some ways, but can also be detrimental.  If you’re targeting a special population, then you probably want to find the users yourself.

Chalkmark has a very specific purpose, seeing where people click on an image when given an instruction. E.g. you upload an image of your web site and tell them “click on the link to update your settings”.  Wherever they click gets recorded, along with everyone else’s clicks on the task, to create a heat map on the image.  I guess it’s useful if you’re carefully testing out the layout of a site across a large population, but usually a small sample suffices and you would get better data with the other tools.

Remember, you are not the user and your assessments of the usability of what you made are likely way off.  Test with real users.  These tools make it easy.