The Core Function
Action lines, also known as scene description, are the prose of a screenplay. They describe what the audience sees and hears. This element bridges the scenes, sets the stage, and describes the crucial physical movements and events that occur outside of dialogue. It is the writer’s tool for directing the ‘movie in the reader’s head.‘
Standard Industry Formatting
Action lines are written in the present tense and formatted in standard paragraph style, aligned to the left margin. They appear directly below a slugline and before any character’s dialogue.
INT. LIBRARY - NIGHT
Dust motes dance in the single beam of a FLASHLIGHT.
SARAH (20s), terrified, creeps along a towering aisle of books. She holds the flashlight with a trembling hand.
A floorboard CREAKS behind her. She freezes, her eyes wide.Best Practices and Common Mistakes
- Write Visually and Concisely: Describe what we see, not what characters are thinking or feeling internally. Show, don’t tell. Keep paragraphs short—ideally no more than 3-4 lines each. White space on the page is your friend.
- Use the Present Tense: Always write action in the present tense (e.g., “John runs,” not “John ran”). This creates a sense of immediacy.
- Introduce Characters Properly: The first time a character appears, their name should be in ALL CAPS, usually followed by their age and a brief, evocative description.
- Capitalize Key Elements: Use ALL CAPS sparingly to draw attention to plot-critical props, sounds, or visual effects.
- Avoid Directing on the Page: Don’t describe camera angles (
The camera pans...) or editing choices (We cut to...). Describe what is happening in the scene, and let the director and editor do their jobs.
Why It Matters
Clear, evocative action lines are what make a screenplay a compelling read. They are the blueprint for the director, cinematographer, production designer, and sound designer. A script with dense, unfilmable, or poorly written action lines is the hallmark of an amateur and is unlikely to be taken seriously.