> For the complete documentation index, see [llms.txt](https://docs.internetobject.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.internetobject.org/structure-and-syntax/values/booleans.md).

# Booleans

A **boolean** is a logical value, either true or false. Booleans are scalar values used for flags, binary states, and conditions.

Each value has a compact and a verbose form, letting you trade brevity for explicitness.

## Syntax

```ebnf
boolean        = compactBoolean | verboseBoolean
compactBoolean = "T" | "F"
verboseBoolean = "true" | "false"
```

## Structural elements

| Token   | Name          | Description               |
| ------- | ------------- | ------------------------- |
| `T`     | Compact true  | `true` in compact form    |
| `F`     | Compact false | `false` in compact form   |
| `true`  | Verbose true  | the verbose true keyword  |
| `false` | Verbose false | the verbose false keyword |

## Valid forms

The compact and verbose forms are equivalent; the compact form is recommended for terse data.

```ruby
---
T, F, true, false
```

## Not a boolean

Boolean keywords are **case-sensitive and spelled exactly**. Any other token is not an error — it is parsed as a different value type, so it is *not* a boolean:

```ruby
t                    # open string "t", not true
TRUE                 # open string "TRUE", not true
True                 # open string "True", not true
1                    # the number 1, not true
0                    # the number 0, not false
```

> Under a `bool` schema, a non-boolean value fails validation with `not-a-bool`. Without a schema, the values above are simply kept as their parsed type (string or number).

## See Also

* [Value Representations](/structure-and-syntax/values.md) — all value types
* [Nulls](/structure-and-syntax/values/null.md) — the absence of a value
* [Bool](/schema-definition-language/data-types/bool.md) — the boolean schema type


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