FLX language provides the following basic data types. The data types of FLX VM are implemented using corresponding Kotlin data types.

- Boolean type with values: true and false
- Null corresponding the nil value in Lisp and null value in Kotlin. However in FLX, the null value is an object unlike in Kotlin.
- Numeric types:
- Double
- Float
- Int
- Long
- Byte
- String
- Char
- List : Implemented using Kotlin’s List<Any>
- Set : Implemented using Kotlin’s Set<Any>
- Array : Implemented using Kotlin’s Set<Any>
- Map : Implemented using Kotlin’s Map<Any, Any>