---
id: built-in-types
title: Built-in types
---
# Built-in Types
TypeSpec Standard Library provide some built-in types that can be used to build more complex types.
Built in types are related to each other according to the rules described in [type relations](../language-basics/type-relations.md).
## Numeric types
| Type | Range | Description |
| ------------ | ------------------------------------------------------------------------------------------------------------ | ----------------------------------------- |
| `numeric` | | Parent type for all numeric types |
| `integer` | | A whole-number |
| `float` | | A binary number |
| `int64` | `-9,223,372,036,854,775,808` to `9,223,372,036,854,775,807` | A 64-bit integer |
| `int32` | `-2,147,483,648` to `2,147,483,647` | A 32-bit integer |
| `int16` | `-32,768` to `32,767` | A 16-bit integer |
| `int8` | `-128` to `127` | A 8-bit integer |
| `safeint` | <code>−9007199254740991 (−(2<sup>53</sup> − 1))</code> to <code>9007199254740991 (2<sup>53</sup> − 1)</code> | An integer that can be serialized to JSON |
| `uint64` | `0` to `18,446,744,073,709,551,615` | Unsigned 64-bit integer |
| `uint32` | `0` to `4,294,967,295` | Unsigned 32-bit integer |
| `uint16` | `0` to `65,535` | Unsigned 16-bit integer |
| `uint8` | `0` to `255 ` | Unsigned 8-bit integer |
| `float32` | <code> ±1.5 x 10<sup>45</sup></code> to <code>±3.4 x 10<sup>38</sup></code> | A 32 bit floating point number |
| `float64` | <code>±5.0 × 10<sup>−324</sup></code> to <code>±1.7 × 10<sup>308</sup></code> | A 64 bit floating point number |
| `decimal` | | A decimal number |
| `decimal128` | 34 decimal digits with an exponent range from `-6143` to `6144` | A 128 bit decimal number |
## Date and time types
| Type | Description |
| ---------------- | ----------------------------------------------------------------------------------- |
| `plainDate` | A date on a calendar without a time zone, e.g. "April 10th" |
| `plainTime` | A time on a clock without a time zone, e.g. "3:00 am" |
| `utcDateTime` | A date and time in coordinated universal time (UTC), e.g. "1985-04-12T23:20:50.52Z" |
| `offsetDateTime` | A date and time in a particular time zone, e.g. "April 10th at 3:00am in PST" |
| `duration` | A duration/time period. e.g 5s, 10h |
## Other core types
| Type | Description |
| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `bytes` | A sequence of bytes |
| `string` | A sequence of textual characters |
| `boolean` | Boolean with `true` and `false` values |
| `null` | Null value |
| `Array<T>` | Array model type, equivalent to `T[]` |
| `Record<T>` | Model with string keys where all the values have type `T` (similar to `Map<string, T>` in TypeScript or `Dictionary<string, T>` in .Net) |
| `unknown` | A top type in TypeSpec that all types can be assigned to. Values that can have any type should be assigned this value (similar to `any` in JavaScript) |
| `void` | A function/operation return type indicating the function/operation doesn't return a value. |
| `never` | The never type indicates the values that will never occur. |
## String types
Built-in types that are known string formats
| Type | Description |
| ----- | ------------ |
| `url` | A url String |microsoft/typespec
Publicmirrored from https://github.com/microsoft/typespecAvailable
docs/language-basics/built-in-types.md
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