| UnableToSetCookie | Test.WebDriver.Exceptions, Test.WebDriver.Types, Test.WebDriver |
| Uncached | Test.WebDriver.Commands, Test.WebDriver.Types, Test.WebDriver |
| unexpected | Test.WebDriver.Commands.Wait |
| UnexpectedAlertBehavior | Test.WebDriver.Capabilities, Test.WebDriver.Types |
| unexpectedAlertBehavior | Test.WebDriver.Capabilities, Test.WebDriver.Types, Test.WebDriver |
| UnexpectedAlertOpen | Test.WebDriver.Exceptions, Test.WebDriver.Types, Test.WebDriver |
| unionProfiles | Test.WebDriver.Common.Profile, Test.WebDriver.Firefox.Profile |
| Unix | Test.WebDriver.Capabilities, Test.WebDriver.Types, Test.WebDriver |
| UnknownCommand | |
| 1 (Type/Class) | Test.WebDriver.Exceptions, Test.WebDriver.Types, Test.WebDriver |
| 2 (Data Constructor) | Test.WebDriver.Exceptions, Test.WebDriver.Types, Test.WebDriver |
| UnknownError | Test.WebDriver.Exceptions, Test.WebDriver.Types, Test.WebDriver |
| UnknownFrame | Test.WebDriver.Exceptions, Test.WebDriver.Types, Test.WebDriver |
| UpdateReady | Test.WebDriver.Commands, Test.WebDriver.Types, Test.WebDriver |
| uploadFile | Test.WebDriver.Commands, Test.WebDriver |
| uploadRawFile | Test.WebDriver.Commands, Test.WebDriver |
| uploadZipEntry | Test.WebDriver.Commands, Test.WebDriver |
| urlEncode | Test.WebDriver.Utils |
| UseSystemSettings | Test.WebDriver.Capabilities, Test.WebDriver.Types, Test.WebDriver |