Slugline Formatting: Meaning & Definition in Film

The Core Function

A slugline is the functional heading for a new scene. Its purpose is to instantly orient the reader—and every member of a production crew—to a new setting. Every time the location or time of day changes in a meaningful way, a new slugline is required. It is the primary organizational element of a screenplay.

Standard Industry Formatting

A slugline is always written in all capital letters and consists of three essential parts, separated by a space and a hyphen:

1. INT. or EXT.: Specifies whether the scene is an INTerior or EXTerior location. This is a critical piece of information for lighting, sound, and production design.
2. LOCATION: The specific place where the scene occurs (e.g., DINER, JAKE’S APARTMENT, ABANDONED WAREHOUSE).
3. TIME OF DAY: The time the scene takes place. This is usually limited to simple descriptors like DAY or NIGHT. More specific times like DUSK, DAWN, or LATER can be used if they are narratively significant.

Here are some correctly formatted examples:

INT. COFFEE SHOP - DAY

EXT. CITY STREET - NIGHT

INT. SPACESHIP COCKPIT - CONTINUOUS

Best Practices and Common Mistakes

• Be Concise: The location should be as brief as possible while still being clear. INT. JAKE'S MESSY APARTMENT - DAY is incorrect; the ‘messy’ detail belongs in the action lines.
• Be Consistent: If you call a location INT. JAKE'S APARTMENT - DAY once, use that exact same phrasing every time you return to it.
• Only Slugline When Necessary: Don’t create a new slugline if a character is simply moving from one part of a continuous location to another (e.g., from the living room to the kitchen). Use a subheader or describe the movement in the action lines.

Why It Matters

The slugline is the single most important element for a script breakdown. The assistant director uses sluglines to create a shooting schedule. The line producer uses them to create a budget. The location manager uses them to scout locations. The director of photography and gaffer use them to plan lighting. Inconsistent or unclear sluglines create confusion and can lead to costly production errors.