According to many dictionaries including merriam-webster , update is a transitive verb. So I expect the following sentence (used in Firefox) to be incorrect: Please wait while Firefox is updating. I think Firefox is the object of this sentence and it should have been used like this: Please wait while Firefox is being updated. Is the first sentence grammatically correct? Answer "To update" is an example of an ambitransitive verb, which can be used with or without an object. In the intransitive case, it certainly feels like the pronoun "itself" is implied, but that's not generally how this kind of phrase is considered. Consider a more commonplace, less technical example, "to shave": In Penny Lane, the barber shaves another customer. John is shaving right now. In other languages - Spanish comes to mind - you would need a reflexive pronoun ( se ) in the second sentence (and in your Firefox sentence), but in English it's not necessary. After a bit o...