I was wondering if there was a specific dictionary that includes fields to specify if a word is primarily used in spoken language as opposed to written.
For example written works use 将 whereas spoken uses 把。
I think the Tuttle Learner's Dictionary or the free Pleco C-E Dictionary, and others, should contain such information where it is clear-cut. (They aren’t specifically for that; I would guess 98% of all vocabulary can be used for both spoken and written language, such that a dedicated field for usage wouldn‘t add much information most of the time.)
If you have access to a library or are willing to order the book, you could also have a look at this book recommendation by sobriaebritas. It contains a lot of vocabulary-related information, including register.