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+# nlohmann::basic_json::number_unsigned_t
+
+```
+using number_unsigned_t = NumberUnsignedType;
+```
+
+The type used to store JSON numbers (unsigned).
+
+[RFC 8259](https://tools.ietf.org/html/rfc8259) describes numbers as follows:
+
+> The representation of numbers is similar to that used in most programming languages. A number is represented in base 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.
+
+This description includes both integer and floating-point numbers. However, C++ allows more precise storage if it is known whether the number is a signed integer, an unsigned integer, or a floating-point number. Therefore, three different types, [`number_integer_t`](https://json.nlohmann.me/api/basic_json/number_integer_t/index.md), `number_unsigned_t` and [`number_float_t`](https://json.nlohmann.me/api/basic_json/number_float_t/index.md) are used.
+
+To store unsigned integer numbers in C++, a type is defined by the template parameter `NumberUnsignedType` which chooses the type to use.
+
+## Notes
+
+#### Default type
+
+With the default values for `NumberUnsignedType` (`std::uint64_t`), the default value for `number_unsigned_t` is `std::uint64_t`.
+
+#### Default behavior
+
+- The restrictions about leading zeros are not enforced in C++. Instead, leading zeros in integer literals lead to an interpretation as an octal number. Internally, the value will be stored as a decimal number. For instance, the C++ integer literal `010` will be serialized to `8`. During deserialization, leading zeros yield an error.
+
+#### Limits
+
+[RFC 8259](https://tools.ietf.org/html/rfc8259) specifies:
+
+> An implementation may set limits on the range and precision of numbers.
+
+When the default type is used, the maximal integer number that can be stored is `18446744073709551615` (UINT64_MAX) and the minimal integer number that can be stored is `0`. Integer numbers that are out of range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers will automatically be stored as [`number_integer_t`](https://json.nlohmann.me/api/basic_json/number_integer_t/index.md) or [`number_float_t`](https://json.nlohmann.me/api/basic_json/number_float_t/index.md).
+
+[RFC 8259](https://tools.ietf.org/html/rfc8259) further states:
+
+> Note that when such software is used, numbers that are integers and are in the range [-2^{53}+1, 2^{53}-1] are interoperable in the sense that implementations will agree exactly on their numeric values.
+
+As this range is a subrange (when considered in conjunction with the `number_integer_t` type) of the exactly supported range [0, UINT64_MAX], this class's integer type is interoperable.
+
+#### Storage
+
+Integer number values are stored directly inside a `basic_json` type.
+
+## Examples
+
+Example
+
+The following code shows that `number_unsigned_t` is by default, a typedef to `std::uint64_t`.
+
+```
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    std::cout << std::boolalpha << std::is_same<std::uint64_t, json::number_unsigned_t>::value << std::endl;
+}
+```
+
+Output:
+
+```
+true
+```
+
+## Version history
+
+- Added in version 2.0.0.