Scalar types are basic atomic data types in GraphQL that represent single values. They include types like String for text, Int for integers, Float for floating-point numbers, Boolean for true or false values, and ID for unique identifiers. Scalars are used to represent the leaves of the GraphQL query tree, serving as the foundation for more complex data structures. Scalar types represent primitive leaf values in a GraphQL type system. GraphQL responses take the form of a hierarchical tree; the leaves of this tree are typically GraphQL Scalar types (but may also be Enum types or null values). GraphQL provides a number of built-in scalars.
Int: A signed 32‐bit integer.
Float: A signed double-precision floating-point value.
String: A UTF‐8 character sequence.
Boolean: true or false.
In most GraphQL service implementations, there is also a way to specify custom Scalar types.
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ID: A unique identifier, often used to refetch an object or as the key for a cache. The ID type is serialized in the same way as a String; however, defining it as an ID signifies that it is not intended to be human‐readable.
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