16. The one or more non-transitory computer-readable media of claim 15 , wherein the operations comprise determining, by the one or more computers, a quantity of alternative transcriptions for the utterance to provide for display, the quantity of alternative transcriptions being fewer than all of the speech recognition candidates for the utterance; wherein providing the subset of speech recognition candidates comprises providing a subset of the speech recognition candidates having the determined quantity of speech recognition candidates.
15. One or more non-transitory computer-readable media storing instructions that, when executed by one or more computers, cause the one or more computers to perform operations comprising: obtaining, by the one or more computers, acoustic data for an utterance; determining, by the one or more computers, speech recognition candidates for the utterance based on the acoustic data; obtaining, by the one or more computers, a ranking of the speech recognition candidates determined by a speech recognizer; selecting, by the one or more computers, a transcription for the acoustic data from among the speech recognition candidates; determining, by the one or more computers, feature scores from the ranking of the speech recognition candidates; generating, by the one or more computers, a classifier output for each of at least some of the speech recognition candidates, wherein each of the classifier outputs is an output that a trained machine learning classifier provided in response to receiving at least one of the feature scores as input; selecting, by the one or more computers, a subset of the speech recognition candidates based on the classifier outputs of the trained machine learning classifier; and providing, by the one or more computers and for display at a client device, data indicating (i) the transcription for the utterance and (ii) the subset of the speech recognition candidates as a set of alternative transcriptions for the utterance, wherein the one or more computers are configured to provide different quantities of alternative transcriptions for different utterances.