Typed communication can appear in italics or it can be punctuated with regular quotation marks, the same way you would spoken dialogue. If you use quotation marks, tags like “she typed” or “she said” are quick and easy ways to keep the mode of communication clear. Also, look for ways you can set up the situation through narrative, using details specific to the method of communication:
Fingers poised over the keyboard, he looked at the words he’d written: “Glad you found me.” Did that seem right? He hadn’t expected to hear from her so soon and now he felt rushed. She knew he had seen her message.
Regardless of format and punctuation choices, consider the ways in which spoken dialogue and typed communication differ. Language in typed forms of communication often takes on its own defining characteristics. Private messages sound different than spoken dialogue. And text messages have their own short hand. In “Pure Language” in A Visit from the Good Squad, Jennifer Egan invents a future in which characters T each other through handsets. The language used in Ts is highly individualized to that form of communication. Look at this exchange between Alex and his employee Lulu:
U hav sum nAms 4 me? he read on the screen.
hEr thA r, Alex typed, and flushed the list of fifty contacts, along with notes, tips on angles of approach, and individual no-nos, into Lulu’s handset.
GrAt. Il gt 2 wrk.
Capturing the nuances of each mode of communication will help your readers better understand how your characters are communicating in any given scene and lend exchanges vital authenticity.