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.

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	−9007199254740991 (−(253 − 1)) to 9007199254740991 (253 − 1)	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	±1.5 x 1045 to ±3.4 x 1038	A 32 bit floating point number
float64	±5.0 × 10−324 to ±1.7 × 10308	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

Numeric supertypes

numeric, integer, float and decimal are types that represent any possible number in their category. For some emit targets, BigInt or BigDecimal might be an analogous type satisfying the TypeSpec types integer and decimal respectively. For other targets where the language, serialization format, or protocol does not support an analogous type, emitters may decide on a policy for emitting the numeric supertypes. This might involve picking the closest analogous type and reporting a warning when they are encountered.

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<Element>	Array model type, equivalent to Element[]
Record<Element>	Model with string keys where all the values have type Element (similar to Map<string, Element> in TypeScript or Dictionary<string, Element> 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