While great action lines and dialogue are the hallmark of professional screenplay formatting, don’t take slug lines for granted. As the introduction to your settings and scenes, the right slug can make a world of difference for the reader.
A slug line (also known as a scene heading) establishes the setting of each scene. It lets the reader know when a new scene begins, and where and when it takes place. Knowing these details ahead of time helps the reader visualize the elements of the film.
Slugs also serve as an important tool when the production team breaks down the script and determines logistics—such as the number of locations, how many day and night scenes there are, budget, and scheduling for cast and crew.
The proper slug line format is one line, all uppercase letters, indicating three elements:
- Interior (INT.) or exterior (EXT.)
- Time of day (most commonly “day” or “night”)
Take a look at this slug line example from the script for “The Banshees of Inisherin” by Martin McDonagh.
Immediately, you can determine the following:
- “INT.”: This is an interior scene.
- “PUB”: The location is a pub.
- “DAY”: This scene takes place during the day.
Slug lines come in two forms: master scene headings and subheadings.
Master scene headings are the primary type of slug line. They indicate a new scene is starting, letting the reader know where and when they are. If your script has 50 scenes, then it’ll have 50 master scene headings. A typical master scene heading looks like this one, from the script for “Women Talking” by Sarah Polley. We’re inside a barn and it’s morning:
Occasionally, two scenes will take place back to back in the same location, with time passing in between them. In this case, you’d add indicators such as “LATER.” Take this scene, from the script for “Aftersun” by Charlotte Wells, which starts on a bus:
The next scene opens on the same bus, but a good amount of time has passed:
In some specific cases, you can include INT./EXT. at the start of your master scene heading to indicate the action will be switching between both seamlessly. This could be a conversation through an open window, for instance, or a scene like this one in Steven Spielberg and Tony Kushner’s script for “The Fabelmans” that takes place in a moving car:
While master scene headings establish the location and time of a scene, subheadings indicate a change of location within that same scene. Subheadings are still in all capital letters, but often don’t indicate interior/exterior or time of day.
For example: Bong Joon Ho and Han Jin-won’s script for “Parasite” opens with the scene heading: INT. SEMI-BASEMENT - DAY. After establishing that we’re inside a house, the writers then use subheadings to move to other rooms.
Some scenes are complex, switching between locations—and between interiors and exteriors—all within the same continuous sequence. In this case, add “CONTINUOUS” to your slug lines, as seen in the script for “Black Panther: Wakanda Forever” by Ryan Coogler and Joe Robert Cole.
Learning how to write succinct, informative slug lines is vital to becoming a successful screenwriter. In this medium, clarity is key. Great slug lines will keep your readers glued to the page and able to envision the story you’ve crafted.