---
title: Writing reels
description: How a reel is laid out: what it records, its setup, and the steps it plays.
url: https://docs-v3-preview.elastic.dev/reel/reels
---

# Writing reels
A reel is a `.reel` file, one command per line, in three parts:
```
# 1. What it records: the first line (after any Import lines and comments).
Launch ~/Projects/musicbox/build/App/Musicbox.app

# 2. Setup: what to write and how. Nothing is recorded yet.
Output musicbox.mp4
Set Size 1440x900
Intro "Musicbox" "Chord progressions, sketched and heard"

# 3. Steps: recording starts at the first one.
Wait #lanes
Key space
Say "The chords lane drives the others."
```

- **What it records.** `Launch` an app, by bundle id or path, or `Open` a web page. Everything after is read knowing
  which, so a setting for the other kind (`Set Viewport` in an app reel, `Set Size` in a web reel) is refused at its
  line rather than ignored.
- **Setup** is `Output`, `Set`, `Intro`, `Outro` and `Profile`, before the first step. A reel needs at least one
  `Output`.
- **Steps** are everything else: `Click`, `Type`, `Key`, `Say`, `Caption`, `Zoom`, and the rest. See
  [Commands](https://docs-v3-preview.elastic.dev/reel/reference/commands).


## Comments

`#` starts a comment at the start of a line, or after a space:
```
Set Size 1440x900  
Click #play         # #play here is an identifier, not a comment
```

`#` straight after a word is part of it: `#play` is an element's identifier and `#1d2b3a` a colour.

## Values

- **Durations:** `500ms`, `2s`, `1.5s`, `1m`, or a bare number of seconds.
- **Text** in double quotes: `Type "hello"`, `Caption "Saved"`. `\n` is return, `\"` a quote.
- **Options** after `@` on the command: `Type@20ms "fast"`, `Say@over "…"`, `Zoom@ease-out,600ms #list`,
  `Intro@slide-up "Title"`.


## When a line is wrong

reel reads the whole reel before it records anything, and an error names its line:
```
$ reel check demo.reel
Error: line 7: 'cmd+nope' is not a key; write a key name such as return or a, with modifiers: cmd+s
```

`reel check` reads a reel and says what it would do: what it launches, the narration, how many actions and
captions, and every file it would write, for each profile.

|                                                                     |                                                                   |
|---------------------------------------------------------------------|-------------------------------------------------------------------|
| [Elements](https://docs-v3-preview.elastic.dev/reel/reels/elements) | How a reel names what to click, wait for and zoom on.             |
| [Paths](https://docs-v3-preview.elastic.dev/reel/reels/paths)       | Relative paths, `~`, and `//` for the root of the git repository. |