1. A method comprising: outputting, by a computing device and for display, a graphical keyboard; receiving, by the computing device, an indication of input; selecting, by the computing device and based at least in part on the indication of the input, a plurality of respective keys of the graphical keyboard; responsive to selecting the plurality of respective keys, classifying, by the computing device, a plurality of respective characters associated with the plurality of respective keys into a category based at least in part on one or more of the plurality of respective characters matching at least one metacharacter that corresponds to a format for the category, wherein at least one character of the plurality of respective characters comprises at least one of a number or a non-alphabetic symbol; determining, by the computing device and based at least in part on a language model, at least one candidate character string that corresponds to the category, such that the at least one candidate character string is based at least in part on the format for the category, wherein the language model comprises data indicating a probability of at least one character string based on the indication of input; and outputting, by the computing device, for display, and based on determining the at least one candidate string that corresponds to the category, the at least one candidate character string.