> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/colinhacks/zod/llms.txt
> Use this file to discover all available pages before exploring further.

# z.boolean()

> Boolean schema type

## Basic Usage

```typescript theme={null}
import { z } from 'zod';

const schema = z.boolean();
schema.parse(true); // true
schema.parse(false); // false
schema.parse("true"); // throws ZodError
schema.parse(1); // throws ZodError
```

## Type Signature

```typescript theme={null}
function boolean(params?: string | $ZodBooleanParams): ZodBoolean
```

<ParamField path="params" type="string | $ZodBooleanParams" optional>
  Optional error message (string) or configuration object
</ParamField>

## Behavior

`z.boolean()` only accepts literal `true` and `false` values. It does NOT perform type coercion:

```typescript theme={null}
const schema = z.boolean();

// Valid
schema.parse(true); // true
schema.parse(false); // false

// Invalid - throws ZodError
schema.parse("true");
schema.parse("false");
schema.parse(1);
schema.parse(0);
schema.parse(null);
schema.parse(undefined);
```

## Type Coercion

If you need to accept truthy/falsy values, use coercion:

```typescript theme={null}
import { z } from 'zod';

const schema = z.coerce.boolean();

schema.parse(true); // true
schema.parse(false); // false
schema.parse("true"); // true
schema.parse("false"); // false
schema.parse(1); // true
schema.parse(0); // false
schema.parse("yes"); // true
schema.parse(""); // false
```

## Usage with Optional

```typescript theme={null}
const optionalBoolean = z.boolean().optional();

optionalBoolean.parse(true); // true
optionalBoolean.parse(false); // false
optionalBoolean.parse(undefined); // undefined
```

## Usage with Nullable

```typescript theme={null}
const nullableBoolean = z.boolean().nullable();

nullableBoolean.parse(true); // true
nullableBoolean.parse(false); // false
nullableBoolean.parse(null); // null
```

## Default Values

```typescript theme={null}
const withDefault = z.boolean().default(false);

withDefault.parse(true); // true
withDefault.parse(undefined); // false (default applied)
```

## Custom Error Messages

```typescript theme={null}
const schema = z.boolean("Must be a boolean value");

// Or with object syntax
const schema2 = z.boolean({
  message: "Must be a boolean value"
});
```

## TypeScript Type

```typescript theme={null}
import { z } from 'zod';

const schema = z.boolean();
type BooleanType = z.infer<typeof schema>; // boolean
```

## Refinements

While uncommon, you can add refinements to boolean schemas:

```typescript theme={null}
const mustBeTrue = z.boolean().refine(val => val === true, {
  message: "Value must be true"
});

mustBeTrue.parse(true); // true
mustBeTrue.parse(false); // throws
```

## See Also

* [z.coerce.boolean()](/api/coercion#boolean) - Boolean with type coercion
* [Literals](/api/literals) - For accepting specific boolean values
* [Optional](/api/wrappers/optional) - Making booleans optional