Action Lines (Description)
Action lines (sometimes called description or direction) are the prose passages that describe everything the audience sees and hears that is not dialogue. They set scenes, move characters through space, create atmosphere, and carry the visual weight of your story.
Great action writing is invisible. The reader does not notice it - they just see the movie playing in their head.
Writing Action
The purpose of action lines is to communicate what the camera would capture. Not what a character is thinking. Not the backstory of a location. Not the thematic significance of a moment. Action lines describe observable reality: what is visible, what is audible, and what is physically happening in the scene.
If you come from prose fiction, this requires a shift in thinking. In a novel, you have access to a character's interior life. In a screenplay, you have access to their behavior.
We do not know why Amir is in a hurry, where he is going, or what is in the bag. But we know he is anxious, prepared, and that something is about to happen. The action creates tension through behavior alone.
Good action writing has a rhythm. Short sentences create speed and urgency. Longer sentences slow the pace and invite the reader to take in the environment. Vary sentence length and you control how quickly the reader moves through the page.
Present Tense Always
Screenplays are written in present tense, without exception. "He walks" not "He walked." "The building explodes" not "The building exploded." "Rain falls" not "Rain was falling." This is not a stylistic choice. It is a fundamental convention of the form.
Present tense creates immediacy. The reader experiences the story as it happens, in real time. No filter of memory or reflection between them and the action. This is how a movie works, and the screenplay mirrors that experience on the page.
Notice how the present tense puts you directly into the scene. "She stops, braces her hands on her knees, and looks back" feels immediate. "She stopped, braced her hands on her knees, and looked back" reads like a recollection, not a lived experience.
Keep It Visual
Every sentence in your action lines should describe something that can be photographed or recorded. If a camera cannot capture it, it does not belong in the script.
This rule eliminates several categories of writing that are common in amateur screenplays: internal thoughts ("She wonders if she made the right choice"), backstory ("This is the house where he grew up, before the accident"), editorializing ("It is a beautiful day, the kind that makes you glad to be alive"), and abstract statements ("The room feels dangerous").
Instead, make the abstract concrete. Do not write that a room "feels dangerous." Describe what makes it feel dangerous:
The reader knows this room is dangerous because of what they see: the swinging light, the decay, the tools that could be weapons, the disturbing neatness of their arrangement. You did not tell the reader to feel dread. You gave them the details that produce it.
The same principle applies to character emotions. Do not write "John is angry." Write what John does when he is angry:
Breaking Up Action
One of the most visible differences between amateur and professional screenplays is paragraph density. Amateur scripts tend toward heavy blocks of description - five, six, seven lines crammed into a single paragraph. Professional scripts break action into short, focused bursts, rarely exceeding three or four lines.
Readers process short paragraphs faster. White space on the page creates a feeling of pace and movement. And each paragraph break signals a new beat: a shift in visual focus, a new piece of information, or a change in energy.
Consider this dense block:
Now the same content, broken into beats:
The second version contains nearly the same information but reads twice as fast. Each paragraph is a distinct visual beat: the environment, the protagonist's entrance, the reveal of the other character. The white space between paragraphs mirrors the cuts of a finished film.
Paragraph length also controls pacing. During a tense sequence, use very short paragraphs, even single sentences, to create a staccato rhythm:
Each line is a beat. Each line ratchets the tension. The white space between them creates pauses that the reader fills with dread.
Introducing Characters
When a character appears for the first time, their name is written in ALL CAPS within the action lines. This lets casting, wardrobe, hair and makeup, and every other department quickly identify every character in the script and where they first appear.
After the first appearance, the character's name is written normally (not in caps) in action lines, though it stays in caps in the character cue above their dialogue. The capitalization only applies to the first mention in action. It signals "this is someone new."
GRACE KIMURA gets her name in caps, an age range, and two defining details: her stillness amid chaos and the crooked press badge she ignores. We know she is focused, confident, and possibly a little worn down. TOMMY BELL gets a briefer introduction - "too much energy and not enough experience" tells us everything about him in six words.
What to leave out: exhaustive physical descriptions. Do not catalog a character's height, weight, hair color, eye color, clothing, and body type unless a specific detail is essential to the story. If a character's scar is a plot point, mention the scar. If their eye color is not, leave it out.
The best character introductions capture personality, not appearance. Here are a few approaches that work:
You know who these people are without knowing what they look like.
Sound and Emphasis
ALL CAPS in action lines serve two purposes: introducing characters (covered above) and emphasizing important sounds. When a sound is significant to the story - a GUNSHOT that breaks the silence, a KNOCK at the door, the SCREECH of tires - capitalizing it makes sure the sound department and the reader both register its importance.
The capitalized sounds (THUD, KNOCKS) stand out from the surrounding text and tell the reader these are not ambient noise. They are story-critical sounds that drive the scene forward.
Some writers also use caps to emphasize a crucial visual element: a weapon, a clue, an object that will become significant later. This is fine but should be used with restraint. If you capitalize a prop, you are making a promise to the reader that it matters. If it does not pay off later, the emphasis will feel like a false alarm.
The caps on "A CASSETTE TAPE" tell the reader to pay attention. Their brain flags it, stores it, and will remember it when it reappears. Used well, selective emphasis is powerful. Used carelessly, it becomes noise.
Underlining and Bold
Traditional screenplay format does not use bold or italic text in action lines. Some modern screenwriters have adopted bold for emphasis, particularly in action-heavy genres, but it departs from the standard. If you are writing on spec and submitting to agents or contests, stick to the basics: present tense, ALL CAPS for introductions and key sounds, and let your verbs and nouns carry the weight.