TOEFL Practice Online is the only official practice test provided by ETS (the makers of the TOEFL). It's a paid service and each time you order a TOEFL Practice Online, you'll get a different version of the test.
The practice test requires that you download an application and when you run the application, you won't be able to see or open anything else on your screen. This "closed" format helps you concentrate on the test and makes it less likely that you'll look for word definitions online while taking the test.
While the user interface and content is just like a real TOEFL iBT, there are a couple of important differences. While taking the practice test, you can pause the test any time you'd like and come back to it whenever you want. And the Speaking and Writing sections are scored by computer applications as opposed to actual ETS scorers. The practice test uses software called SpeechRater℠ to score your Speaking Section and e-rater® to score your Writing Section.
