How to Write a Slugline (Scene Heading)

A slugline is the uppercase line that begins every scene. It has three parts: whether the scene is interior or exterior, where it takes place, and what time of day it is.

INT. KITCHEN - DAY
EXT. PARKING LOT - NIGHT

That is the entire syntax. The craft is not in the format, which takes a minute to learn. It is in the discipline of naming locations consistently and knowing when a new scene actually starts, because those two decisions propagate into every planning document downstream.

The three parts

INT. or EXT. Interior or exterior, with the full stop. Interior means under a roof; exterior means outside. It exists because the two are fundamentally different production problems: lighting, sound, weather, permits, and control.

Occasionally you need both:

INT./EXT. CAR - DAY

This is standard for vehicle scenes where the camera sees inside and out, and it warns the crew that this is a car rig day, which is its own category of complicated.

The location. The name of the place, in caps. Be specific and, above all, be consistent.

Time of day. DAY or NIGHT, after a hyphen. Keep to these two wherever you possibly can.

Time of day is a budget line

This is the part writers underestimate. Every DAWN, DUSK or MAGIC HOUR you type is a promise that the crew has about twenty usable minutes to get the scene.

• DAY and NIGHT are the workhorses. Use them by default.
• DAWN / DUSK / MAGIC HOUR are real and sometimes essential, but each one constrains the schedule severely. If the story does not genuinely require the light, write DAY.
• CONTINUOUS means this scene runs directly on from the previous one with no time gap.
• LATER or MOMENTS LATER indicates a gap in the same location.

A useful discipline: after finishing a draft, count your non-DAY/NIGHT headings. If there are more than a couple, you have written scheduling problems into the script, and you should be able to justify each one.

Specific, but hierarchical

Write locations from general to specific, separated by a dash or hyphen:

INT. HOSPITAL - WAITING ROOM - DAY
INT. HOSPITAL - CORRIDOR - DAY
INT. HOSPITAL - ROOM 4 - NIGHT

This groups naturally: anyone scheduling can see instantly that these three are all at the hospital and should be shot together, even though they appear in scenes 12, 40 and 78. Write them as WAITING ROOM, CORRIDOR and ROOM 4 with no parent and the relationship is invisible.

The rule: the parent location is the thing you have to book, get permission for, and move the unit to. The child is the specific space within it.

When does a new scene start?

The rule is simple to state and constantly got wrong: a new slugline is needed whenever the location or the time changes.

Not when the topic of conversation changes. Not when a new character arrives. Not when there is a dramatic beat.

So:

• Characters move from the kitchen to the garden: new slugline, because the location changed.
• Characters talk for six pages in one room: one slugline, however long it runs.
• Same room, but we cut to three hours later: new slugline, with LATER or a new time of day.
• A character walks from the hallway into the living room in one continuous move: this is a judgement call. If both spaces are genuinely part of one continuous shot, many writers keep it as one scene. If they are separately dressed and lit spaces, split it.

The reason precision matters here is that scenes are the atomic unit of production. Each one becomes a strip on the stripboard, gets a page count in eighths, gets scheduled, and appears on a call sheet. Merge two scenes that should be separate and the schedule under-counts the work. Split one that should be whole and you have invented a company move that does not exist.

Sub-headers

For brief moves within an established location, a mini-slug or sub-header keeps the page clean:

INT. HOUSE - NIGHT

Sarah moves through the dark.

THE KITCHEN

She opens the fridge. Empty.

THE HALLWAY

A light under the door.

This is legitimate and readable, and experienced writers use it. Be aware that sub-headers are not full scenes, so they may not be picked up as separate entries by a breakdown. For a sequence of quick moves inside one location that will be shot as one setup group, that is exactly what you want. For spaces that genuinely need separate lighting and scheduling, write full sluglines instead.

Things not to put in a slugline

• Camera directions. INT. KITCHEN - CLOSE ON SARAH - DAY is not a scene heading. Describe what matters in the action instead.
• Character names, unless the location genuinely belongs to them and that is how the production will refer to it. SARAH'S APARTMENT is fine and common. SARAH ENTERS THE KITCHEN is not a slugline.
• Story information. EXT. THE BEACH WHERE THEY MET - DAY is a note to yourself, not a heading.
• Time-of-day inventions. - SOMETIME AFTER MIDNIGHT is not schedulable. It is NIGHT.

Scene numbers

Spec scripts do not have scene numbers. They are added when the script is locked for production, and from that point they are permanent.

That permanence is not a technicality. Once scenes are numbered, everything references those numbers: the breakdown, the stripboard, the call sheet, the script supervisor's notes, the camera reports, the edit. If scene 34 is cut during production, the following scenes are not renumbered; 34 simply no longer exists. If a new scene is added between 34 and 35, it becomes 34A.

This is why locking matters, and why renumbering a script mid-production is close to unforgivable.

A quick self-check on your own draft

Run these four passes over a finished draft. Each takes fifteen minutes and each saves days later.

1. List every unique location string. Are any of them the same place written differently? Merge them.
2. Count your DAY versus NIGHT versus everything else. Can any of the exotic ones become DAY or NIGHT without hurting the film?
3. Count your distinct parent locations. Every one is somewhere you have to find, book and travel to. Can any two become one?
4. Check every INT./EXT. Is that scene genuinely both, or did you write it out of uncertainty?

Question 3 is the one that changes budgets. Merging two locations into one on the page, before anyone has scouted anything, is free. Doing it in week three of pre-production is a rewrite.

Next

Sluglines tell us where we are. Next in the chapter: action lines, and the discipline of writing only what the camera can actually record.