Slugline

A slugline, or slug line, is the all-caps scene heading in a screenplay that tells the reader whether a scene is inside or outside, where it takes place and at what time of day.

The standard slugline has three parts on one line, and the most useful version has four:

INT. WALL STREET - TRADING FLOOR - DAY

Two hundred phones ring at once. Traders in shirtsleeves shout across rows of glowing monitors.

Read it left to right and it narrows like a camera pushing in:

• INT. Interior, so we are inside. (EXT. is exterior, outside.)
• WALL STREET The master location, the wider place this scene belongs to.
• TRADING FLOOR The sub-location, the specific room inside it.
• DAY The time of day, which tells the crew how to light it and tells the reader how the world feels.

That order, general to specific, is the whole trick. The reader knows the building before they know the room, and every later scene set anywhere in WALL STREET is filed in the same place.

What a slugline means, and why scripts have them

A slugline, also written slug line and formally called a scene heading, is the capitalised line that starts each new scene in a screenplay. It is the reader's map. Before a single line of action, it answers three questions: are we inside or outside, where are we, and when.

It is also a production document. When a script is scheduled, it is broken down scene by scene, and the sluglines are what get sorted: every scene at the same location is grouped so the crew can shoot them together. That is why the convention is strict. A location spelled two ways becomes two locations on the board, and a missing time of day is a question someone has to come back and ask.

For the person reading your script for a contest, a manager or a producer, sluglines do something simpler. They set the pace. A page with four sluglines reads fast, a scene that runs three pages under one heading reads slow, and a reader feels both before they notice either.

Slugline format: the parts, in order

Every slugline sits on its own line, flush left, in capital letters, with a blank line above it. The parts go in this order, each separated by a hyphen with a space on either side.

1. Interior or exterior. INT. for inside, EXT. for outside, with the period. INT./EXT. (some writers use I/E.) is for a scene that plays both inside and outside at once.
2. The location. As specific as the scene needs. If the place has parts, go general to specific: INT. HOSPITAL - ICU - NIGHT, then INT. HOSPITAL - STAIRWELL - NIGHT.
3. The time. Usually just DAY or NIGHT. Use DAWN, DUSK or SUNSET when the light matters to the scene. Use CONTINUOUS, LATER or MOMENTS LATER when what matters is how this scene connects to the last one.

Anything else, like weather, mood or what the camera does, goes in the action line underneath, not in the heading.

Master sluglines and secondary sluglines

A master slugline is the full heading. A secondary slugline, also called a mini-slug or subheader, is a short heading that marks a move within the scene you are already in, without repeating INT. and the time of day.

INT. WALL STREET - TRADING FLOOR - DAY

MAYA CHEN (29) threads between the desks with a stack of printouts, eyes on the clock above the elevators.

ELEVATOR BANK

The doors slide open. Her boss, GRANT (50s), steps out already talking.

Why it works: Maya has walked twenty feet. A full new heading would suggest a new scene and slow the page down; the mini-slug moves the reader's eye without breaking the flow. Use the same trick for BACK TO SCENE after an insert or a cutaway.

Day, night, CONTINUOUS, LATER and MOMENTS LATER

DAY and NIGHT cover most scenes. The other time words describe the join between two scenes rather than the clock.

INT. WALL STREET - TRADING FLOOR - DAY

Maya snatches the last page off the printer and runs for the stairwell.

INT. WALL STREET - STAIRWELL - CONTINUOUS

She takes the steps two at a time, phone pressed to her ear.

Why it works: CONTINUOUS tells the reader the action carries straight through the cut. It keeps a chase or a walk-and-talk feeling like one unbroken movement.

INT. WALL STREET - TRADING FLOOR - LATER

The floor is empty. One monitor still glows. Maya sits alone at her desk, shoes off.

Why it works: we already know this room, so LATER is all the reader needs. MOMENTS LATER is the short version, for a jump of a few seconds or minutes.

More slugline examples

INT./EXT. for a scene that is inside and outside at once

INT./EXT. MAYA'S CAR - PARKING GARAGE - NIGHT

Maya sits behind the wheel with the door open, one foot on the concrete, playing the voicemail again.

Why it works: the scene lives in the doorway. INT./EXT. saves you from cutting back and forth between two headings for one moment.

A moving car

INT. TAXI - MOVING - NIGHT

Maya in the back seat. The city slides past the window in streaks of neon. The DRIVER watches her in the mirror.

DRIVER

Rough day?

MAYA

(not looking up)

Rough year.

Why it works: MOVING tells the reader, and anyone planning the shoot, that the car is on the road, not parked. If we cut to the outside of the car, that is a new heading: EXT. FDR DRIVE - TAXI - NIGHT.

A flashback

INT. MAYA'S CHILDHOOD KITCHEN - NIGHT (FLASHBACK - 1998)

Ten-year-old MAYA does homework at the table while her FATHER counts bills from a coffee can.

END FLASHBACK.

INT. TAXI - MOVING - NIGHT

Maya opens her eyes.

Why it works: the reader never has to guess which year they are in. The year in the heading marks the way in, and END FLASHBACK marks the way out. Some writers put FLASHBACK at the front of the line instead (FLASHBACK - INT. MAYA'S CHILDHOOD KITCHEN - NIGHT); either is fine if you do it the same way every time. The part that is not optional is closing it. More on when a flashback earns its place.

A montage

MONTAGE - MAYA'S FIRST WEEK

-- Maya at her desk at 6 a.m., the only light on the floor.

-- Maya on three phones at once, writing numbers on her wrist.

-- Maya asleep in the break room, a cold coffee still in her hand.

END MONTAGE

Why it works: a montage compresses time, so it gets one heading instead of a full slugline per image. Keep each shot to a line. SERIES OF SHOTS works the same way on the page and is usually used for a quick run of images inside one event rather than time passing.

A dream

INT. WALL STREET - TRADING FLOOR - NIGHT (DREAM)

The floor is flooded to the knees. Monitors float past, still showing prices. Maya wades toward a phone she can never reach.

INT. MAYA'S APARTMENT - BEDROOM - NIGHT

Maya jolts awake. The phone on her nightstand is ringing.

Why it works: the reader is told up front, so the strange images read as intended rather than as a mistake. If the twist depends on the audience not knowing it is a dream, that is a deliberate choice you are making, and the waking scene has to land the reveal cleanly.

An intercut phone call

INT. WALL STREET - TRADING FLOOR - DAY

Maya grabs the ringing phone.

INT. GRANT'S CAR - MOVING - DAY

Grant drives one-handed, phone wedged against his shoulder.

INTERCUT - MAYA / GRANT

GRANT

Sell it. All of it.

MAYA

Before the close?

Why it works: once both locations have their own slugline, INTERCUT lets the conversation run without a new heading on every line of dialogue.

Slugline examples from a real script: The Runner

The Runner is a feature screenplay by Jeffrey Doka, the editor behind Final Boss Editing. Its first ten pages are an aerial chase: a drug runner's small plane, an F.B.I. plane on its tail, and the desert below. That opening uses twenty-one sluglines in ten pages, and Rich's cockpit gets eight of them, with the location worded the same way every time. Here is how it handles them.

Opening wide and setting the timeline

EXT. U.S. - MEXICO BORDER - DAY (PRESENT)

Mesquite bushes and cacti rush past as we barrel through the empty sky over the desert. The shadow of a small airplane darts across the sand below.

Why it works: the first heading gives the widest possible location, so the reader has the map before anyone speaks. (PRESENT) pins the timeline on page one, which gives any later jump in time a fixed point to jump from.

A moving vehicle with a specific name

INT. RICH'S CESSNA 210 - COCKPIT - DAY (MOVING)

RICH DAVISON (32), a lean, neat pilot-type, sips coffee from a worn thermos and adjusts the collar of his leather flying jacket.

Why it works: the master location is not "PLANE". It is RICH'S CESSNA 210, owner and model. Two planes are about to share this sequence, and this naming means the reader can never mix them up. COCKPIT is the sub-location, and (MOVING) says the plane is in the air.

Moving to another part of the same place

RICH

See us? Our transponder code is thirty fourteen. Yup, transmitting our flight plan now. Only goods--four hundred pounds of car parts. Power steering or something.

A glance into the back seat says otherwise:

INT. RICH'S CESSNA 210 - CARGO AREA - DAY

Four hundred pounds of dried-brown MARIJUANA BALES bound in clear plastic sit on a pallet bolted to the aircraft's frame.

Why it works: same master location, new sub-location. The action line ends on a colon and hands off to the heading, so the cut lands like a punchline: he says car parts, and the slugline takes us straight to what is really back there.

Cutting between two places

INT. F.B.I. BEECHCRAFT BARON - COCKPIT - DAY

SANDRA LLEWELLYN (a well-toned and alert F.B.I. pilot-agent, mid 30s) mans the wheel of the pristine government plane.

SANDRA

There goes our surprise.

INT. RICH'S CESSNA 210 - COCKPIT - DAY

The shadow of the F.B.I. aircraft looms in the back window as James hammers coordinates into the G.P.S. control array.

Why it works: the two headings are built the same way, plane then COCKPIT, so the reader's eye does the comparison for them: pursuer, pursued. Each cut gets a full slugline rather than an INTERCUT because each one has its own action, not just a line of dialogue.

A location with three levels

JAMES

Our plane's got two shadows.

Rich thinks, then jerks his attention to the desert floor.

EXT. AMERICA - NEAR MEXICO BORDER - DESERT BELOW - DAY

The shadows of TWO PLANES dart across the desert sand and shrubs. The larger plane's shadow pursues the other.

Why it works: the heading narrows three times, country, region, then the ground under the planes, and DESERT BELOW tells us exactly where to look. The reveal comes from the change of location, not from anyone explaining it.

One shot holding two aircraft

EXT. OPEN AIR/RICH'S CESSNA/F.B.I. BARON - DAY

The hulking F.B.I. Baron looms behind Rich's light aircraft. His Cessna reaches the apex of its arch.

Why it works: the slashes say this is one shot with both planes in it. It is a less common form; the more usual choice would be something like EXT. SKY OVER THE DESERT - DAY with the action naming both planes. Either works as long as the reader sees one frame, not two.

A time jump to a new place

Hate burns in his voice as Rich mutters:

RICH

Montero.

EXT. KILBOURNE'S HOLE - DESERT AIRSTRIP - DAY - LATER

An expanse of sand surrounds a narrow dirt airstrip. A black volcanic sink-hole scars the ground beside it.

Why it works: LATER skips the landing entirely, and the reader does not miss it. The location was planted two pages earlier, when James suggests a backup landing strip out by Kilbourne's Hole, so when the slugline names it the reader already knows where they are and why.

Common slugline mistakes

• One place, two names. MAYA'S APARTMENT in one scene and MAYA'S FLAT in the next look like two locations to a scheduler and like a new place to a reader. Pick a name and keep it, the way The Runner never lets RICH'S CESSNA 210 become just "the plane".
• A name that can be misread at speed. Readers skim headings. INT. DINER - NIGHT reads as "dinner" at a glance; INT. TRUCK STOP DINER - NIGHT cannot be misread.
• Too few sluglines. If the characters walk into a new place and the heading does not change, the reader is somewhere else before they know it. In one of our script edits, a scene was not clearly a bar until the description, and the fix was the slugline: EXT. LAMPLIGHT BAR - MAIN STREET - NIGHT.
• Too many sluglines. A new full heading every time someone crosses a room chops the scene into pieces. Use a secondary heading instead.
• A flashback with no exit. Mark it going in and coming out, every time. We gave exactly this note in another edit: put FLASHBACK in the slugline and close it with END FLASHBACK.
• CONTINUOUS when time has passed. If there is a gap, it is LATER, or just DAY or NIGHT.
• Story in the heading. INT. KITCHEN - NIGHT - RAIN HAMMERS THE WINDOWS AS SHE WAITS is an action line wearing a heading. Keep the slugline to place and time.
• Camera directions in the heading. CLOSE ON, ANGLE ON and WE SEE belong in a shooting script, if anywhere, not in the scene heading of a spec.

Slug, slugline and scene heading: the other meanings

Outside screenwriting the word turns up in a few other places. In a newsroom, a slug is a short working label for a story, a word or two that follows it from the first draft to the page. In web publishing, a slug is the readable last part of a URL, like slugline at the end of this page's address. Novels have no fixed equivalent: prose does the same job with a scene break, a date line or a strong first sentence that places the reader.

In a screenplay, though, it means one thing: the heading that tells us where and when we are, before anything else happens.

Formatting is the easy part to fix, and it is the first thing a reader notices. If you want a second pair of eyes on a script, a line edit covers the page itself, headings included, and a developmental edit looks at whether the scenes are the right ones. You can get your script edited, free and live on Twitch or privately.

Frequently asked questions

What is a slugline in a script?

A slugline is the line in capital letters that starts every new scene in a screenplay, such as INT. WALL STREET - TRADING FLOOR - DAY. It tells the reader whether the scene is inside or outside, where it is, and when it happens.

Is a slugline the same as a scene heading?

Yes. Slugline, slug line and scene heading all mean the same thing. Screenwriting software usually calls it a scene heading, and writers and readers usually call it a slugline.

What does INT./EXT. mean in a slugline?

INT. means interior (inside) and EXT. means exterior (outside). INT./EXT. is used when a scene plays both inside and outside at once, such as a character sitting in a parked car with the door open, talking to someone on the pavement.

What is the difference between CONTINUOUS and LATER?

CONTINUOUS means no time has passed since the last scene: the character walks straight from one room into the next. LATER means time has passed in the same place. MOMENTS LATER is a short jump, a few seconds or minutes.

When do I need a new slugline?

Write a new slugline whenever the location changes or time jumps. If the characters only move within the same place, a short secondary heading such as KITCHEN or HALLWAY is enough.

How many sluglines should be on a page?

There is no set number. A fast action sequence can have two or three headings a page, and a long dialogue scene can run for several pages under one. Use as many as the reader needs to know where they are, and no more.

Should sluglines be bold or underlined?

The standard is plain capital letters. Some writers bold their sluglines to make them easier to scan, which is accepted, but it is a style choice. Whatever you choose, do it the same way throughout the script.

What is a secondary slugline?

A secondary slugline, sometimes called a mini-slug or subheader, is a short heading such as ELEVATOR BANK or BACK TO SCENE that marks a move within the same scene without repeating the full INT. or EXT. and time of day.