Use O.S. for a speaker who belongs to the current scene but is outside the frame; use V.O. when the voice comes from outside the scene's immediate physical action.
Direct answer
Use O.S. when the character is physically present in the scene's location but not visible in the current frame—for example, calling from the next room. Use V.O. for narration, recordings, thoughts rendered as speech, or a remote voice that is not part of the location's immediate physical space. Because phone and device audio can be styled differently, add a brief source parenthetical when the extension alone could be misread.
On the page
INT. ARCHIVE - NIGHT
Mara searches the dark shelves.
ELI (O.S.)
Third aisle. Blue box.
Her recorder clicks on.
MARA (V.O.)
(on the recording)
Inventory, October fourteenth.
Evidence weight
O.S. keeps a speaker inside the current physical scene; V.O. places the voice outside its immediate on-screen action. That distinction helps readers, performers, editors, and production teams understand what must be captured.
Phone calls are the common edge case. There is no benefit in pretending one extension settles every production convention; choose a consistent house style and name the sound source when ambiguity remains.
Not one rigid template
Some television templates and regional workflows use O.C. (off camera). Follow the delivery template when one is supplied and avoid switching labels mid-draft without a reason.
Some writers use V.O. for a remote caller; others rely on a source parenthetical. “(from the phone)” is useful when V.O. might otherwise read as narration.
A narrator who is not speaking inside the pictured moment is normally marked V.O., even when the narrator also appears elsewhere in the story.
Reader and handoff friction
Choose for the recipient
Choose the extension that lets a reader understand the moment on the first pass. A submission draft does not need a sound-department explanation beyond the voice source the story requires.
The distinction can affect how dialogue is recorded and scheduled. Follow the production's template and script-coordination decisions if they use O.C., filtered dialogue, or another established notation.
In Plot, keep V.O. or O.S. on the character cue and use a short parenthetical only when it adds information, such as “from the phone.” The visible structure stays recognizable as character, parenthetical, and dialogue elements.
Browse the screenplay formatting reference
Complete, source-backed guides for common screenplay situations
Phone calls & intercut
Establish what the audience sees and hears, then use clear scene headings or an INTERCUT instruction so a phone conversation stays easy to picture.
Text messages
Put readable on-screen messages in action, identify the sender when needed, and use one consistent pattern instead of disguising silent text as spoken dialogue.
Montage
Signal the montage, organize its visual beats in action, and end it clearly when the reader might not otherwise know where ordinary scene flow resumes.
