# Schemas

Schemas allow you to validate a specific data type. They are similar to type definitions in TypeScript. Besides primitive values like strings and complex values like objects, Valibot also supports special cases like literals, unions and custom types.

## Primitive values

Valibot supports the creation of schemas for any primitive data type. These are immutable values that are stored directly in the stack, unlike objects where only a reference to the heap is stored.

<ApiList
  label="Primitive schemas"
  items={[
    'bigint',
    'boolean',
    'null',
    'number',
    'string',
    'symbol',
    'undefined',
  ]}
/>

```ts
import * as v from 'valibot';

const BigintSchema = v.bigint(); // bigint
const BooleanSchema = v.boolean(); // boolean
const NullSchema = v.null(); // null
const NumberSchema = v.number(); // number
const StringSchema = v.string(); // string
const SymbolSchema = v.symbol(); // symbol
const UndefinedSchema = v.undefined(); // undefined
```

## Complex values

Among complex values, Valibot supports objects, records, arrays, tuples, and several other classes.

> There are various methods for objects such as <Link href="/api/pick/">`pick`</Link>, <Link href="/api/omit/">`omit`</Link>, <Link href="/api/partial/">`partial`</Link> and <Link href="/api/required/">`required`</Link>. Learn more about them <Link href="/guides/methods/#object-methods">here</Link>.

<ApiList
  label="Complex schemas"
  items={[
    'array',
    'blob',
    'date',
    'file',
    'function',
    'looseObject',
    'looseTuple',
    'map',
    'object',
    'objectWithRest',
    'promise',
    'record',
    'set',
    'strictObject',
    'strictTuple',
    'tuple',
    'tupleWithRest',
  ]}
/>

```ts
import * as v from 'valibot';

const ArraySchema = v.array(v.string()); // string[]
const BlobSchema = v.blob(); // Blob
const DateSchema = v.date(); // Date
const FileSchema = v.file(); // File
const FunctionSchema = v.function(); // (...args: unknown[]) => unknown
const LooseObjectSchema = v.looseObject({ key: v.string() }); // { key: string }
const LooseTupleSchema = v.looseTuple([v.string(), v.number()]); // [string, number]
const MapSchema = v.map(v.string(), v.number()); // Map<string, number>
const ObjectSchema = v.object({ key: v.string() }); // { key: string }
const ObjectWithRestSchema = v.objectWithRest({ key: v.string() }, v.null()); // { key: string } & { [key: string]: null }
const PromiseSchema = v.promise(); // Promise<unknown>
const RecordSchema = v.record(v.string(), v.number()); // Record<string, number>
const SetSchema = v.set(v.number()); // Set<number>
const StrictObjectSchema = v.strictObject({ key: v.string() }); // { key: string }
const StrictTupleSchema = v.strictTuple([v.string(), v.number()]); // [string, number]
const TupleSchema = v.tuple([v.string(), v.number()]); // [string, number]
const TupleWithRestSchema = v.tupleWithRest([v.string(), v.number()], v.null()); // [string, number, ...null[]]
```

## Special cases

Beyond primitive and complex values, there are also schema functions for more special cases.

<ApiList
  label="Special schemas"
  items={[
    'any',
    'custom',
    'enum',
    'exactOptional',
    'instance',
    'intersect',
    'lazy',
    'literal',
    'nan',
    'never',
    'nonNullable',
    'nonNullish',
    'nonOptional',
    'nullable',
    'nullish',
    'optional',
    'picklist',
    'undefinedable',
    'union',
    'unknown',
    'variant',
    'void',
  ]}
/>

```ts
import * as v from 'valibot';

const AnySchema = v.any(); // any
const CustomSchema = v.custom<`${number}px`>(isPixelString); // `${number}px`
const EnumSchema = v.enum(Direction); // Direction
const ExactOptionalSchema = v.exactOptional(v.string()); // string
const InstanceSchema = v.instance(Error); // Error
const LazySchema = v.lazy(() => v.string()); // string
const IntersectSchema = v.intersect([v.string(), v.literal('a')]); // string & 'a'
const LiteralSchema = v.literal('foo'); // 'foo'
const NanSchema = v.nan(); // NaN
const NeverSchema = v.never(); // never
const NonNullableSchema = v.nonNullable(v.nullable(v.string())); // string
const NonNullishSchema = v.nonNullish(v.nullish(v.string())); // string
const NonOptionalSchema = v.nonOptional(v.optional(v.string())); // string
const NullableSchema = v.nullable(v.string()); // string | null
const NullishSchema = v.nullish(v.string()); // string | null | undefined
const OptionalSchema = v.optional(v.string()); // string | undefined
const PicklistSchema = v.picklist(['a', 'b']); // 'a' | 'b'
const UndefinedableSchema = v.undefinedable(v.string()); // string | undefined
const UnionSchema = v.union([v.string(), v.number()]); // string | number
const UnknownSchema = v.unknown(); // unknown
const VariantSchema = v.variant('type', [
  v.object({ type: v.literal('a'), foo: v.string() }),
  v.object({ type: v.literal('b'), bar: v.number() }),
]); // { type: 'a'; foo: string } | { type: 'b'; bar: number }
const VoidSchema = v.void(); // void
```