A few weeks back, I wrote an article explaining how anyone can (nay, should!) run cheap and simple usability tests. Back then, I wrote this:

Even if you don't have any external way of recording a usability test, it should at least be possible to keep some kind of screen capture application running which can also record input from the computer's microphone.

I didn't point out any specific screen recording applications. Although there are quite a few of these applications available for Macs, all of them have certain quirks which can get a bit annoying when running usability tests. None of these applications are aimed specifically at people running usability tests.

Or rather, I should say there were no Mac screen recording applications aimed specifically at people running usability tests; because now, there is one: Clearleft's Silverback.1

What Silverback Does

Silverback is described as "a guerrilla usability testing app for people who design and build websites." This is quite a strange description. I'm not sure why it is described as a "guerilla" application,2 and I'm also not sure why is is targeted at "people who design and build websites." It's just as suitable for people who create native applications.3

What the application does is actually rather basic: It records a computer's iSight and screen. What makes Silverback interesting is that it does so in a way which makes it perfectly suitable for certain types of usability tests.

After launching the application, you are greeted by the extremely well designed main application window.

Silverback after starting up

It is obvious that a lot of thought (and, presumably, testing) has gone into the design of Silverback's user interface. To start working with Silverback, simply set up the application or site you want to test, open Silverback, click on "New Project", name the project, and click on "New Session." You can now enter the test subject's name, add a few notes, adjust the camera, and hit "Start Session" when you're ready.

Silverback after starting up

This wil dim the screen. At this point, you can invite your test subject, prep them for the test, and tell them to hit space to start.

Silverback after starting up

During the test, you can use your Apple Remote to add chapter marks or pause and restart the test. Setting chapter marks is a good idea if you notice an issue during the test; to make sure you remember why you made each chapter mark, you should also keep a written log while the test is running.

Once the test is done, the screen and iSight recordings can be exported as a picture-in-picture QuickTime movie, but can not be viewed immediately within Silverback itself. The exported video will show mouse clicks visually, but you can't add your notes to the chapter marks. You will have to keep track of them separately.

What's Awesome About Silverback

Silverback takes one particular piece of usability testing and makes it dead simple. Until now, recording the screen during a usability session required using tools which were meant for different tasks like producing screencasts. Silverback, on the other hand, is dedicated to usability testing, and does this particular job extremely well.

What's Not So Awesome

You're required to stay with the test subject

In order to use Silverback, you are basically required to look over the test subject's shoulder during the whole test. Having somebody constantly looking at your screen while you're using an application can be annoying or even intimidating and thus influence the test results. Test subjects are often already somewhat nervous as it is, so we try to avoid such situations in our tests.

If you leave the room or move away from the test subject's computer you can't set chapter marks anymore. Silverback does not support remote testing. You can not run tests where the tester is in a different room or sitting far apart from the test subject.

Optimally, Silverback would come as two different applications, one for the tester and one for the test subject. The application running on the tester's computer would show the test subject's screen and allow the tester to add chapter marks with notes while the test is running. Unfortunately, such a solution could potentially harm Silverback's simplicity.

Clearleft's response to this is that such a feature would add complexity and development time and cost to the app, as it would require two-way voice chat as well as streaming the test subject's screen and possibly iSight camera.

You can't watch existing test sessions inside Silverback

While being able to export test sessions as QuickTime movies is extremely important,4 there is no reason why it must be the only way of watching them. Since Silverback already keeps track of your projects and sessions, why not let me watch them within Silverback, where it is possible to dynamically switch between the two pictures as the situation requires?

Clearleft explains:

The screen data is stored as data rather than video, so requires compiling time before viewing. That means there's no way of getting an instant playback within Silverback. In the beta, we showed a preview of only the iSight video (thinking that was better than nothing). We removed that from the release version as it turned out that this confused people, who were expecting a preview of what would be exported.

You can't annotate Chapter Marks

While it's great that you can add chapter marks to your movie, you can't add text to the marks. You will have to keep a separate log outside of Silverback, detailing what each chapter mark meant.


If you're doing basic over-the-shoulder usability tests already, Silverback is an awesome application which makes your job so much easier. If you're doing more sophisticated usability tests, Silverback is probably not yet of much use. Fortunately, Clearleft is considering adding remote tests, but strangely, they have "no plans" for allowing users to watch sessions within Silverback. If you can't watch sessions within Silverback, the project and session management features become a bit pointless; why have these features if you have to store and manage the watchable session videos somewhere else?

Paul Annett from Clearleft told me:

If enough people want remote testing and previewing within the app, we'll be sure to consider it

Having said that, Silverback is still a good, very clean first version of a potentially great application. It's not yet suitable for every type of usability test, but the things it does, it does very well.

Silverback works in Tiger and Leopard and costs 50 bucks, which is a minuscule amount compared to other usability applications and makes it affordable for anyone. What's more, 10% of profits are donated to saving the gorillas.

Further Reading

Nick Finck wrote a great review of Silverback on, while Harry Brignull wrote one on has some inital impressions. has another review. Jochen Wolters has yet another one. There's a screencast on Garrett Dimon has a conversation with Clearleft's Andy Budd.

Note: This blog post was updated with some comments from Paul Annett, Senior Designer at Clearleft.

  1. The application's fantastic icon was designed by Jon Hicks, by the way ↩︎

  2. Paul Annett explained it to me, writing "We've taken [the guerilla] analogy and used it in terms of usability testing - with Silverback runs in the background without the participant noticing, and allows quick and dirty usability testing. It's not designed to be expensive and fully comprehensive. Also, guerilla allows us to make a great pun about gorillas." ↩︎

  3. And actually, the "for people who design and build websites" claim has now disappeared from, but the twitter page still says "Usability testing software for web designers." ↩︎

  4. Many usability tests require creating a movie with some of the issues found and solutions implemented, a kind of executive summary/usability ad. This movie is typically shown to management to explain the importance of usability testing and to show them that the money spent running all these tests is not wasted, but is used to improve the product in very real, tangible ways. Sometimes, such movies are also shown to engineering/R&D in order to convince them that the changes made to the user interface improved the application for end users, and to get them to buy into usability testing. ↩︎

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Want to read more like this? Buy my book's second edition! Designed for Use: Create Usable Interfaces for Applications and the Web is now available DRM-free directly from The Pragmatic Programmers. Or you can get it on Amazon, where it's also available in Chinese and Japanese.