---
title: "nullptr"
ms.date: 07/22/2020
f1_keywords: ["nullptr_cpp"]
helpviewer_keywords: ["nullptr keyword [C++]"]
ms.assetid: e9d80ea6-2506-4eb5-b47b-2349df085832
---
# nullptr

The **`nullptr`** keyword specifies a null pointer constant of type `std::nullptr_t`, which is convertible to any raw pointer type.  Although you can use the keyword **`nullptr`** without including any headers, if your code uses the type `std::nullptr_t`, then you must define it by including the header `<cstddef>`.

> [!NOTE]
> The **`nullptr`** keyword is also defined in C++/CLI for managed code applications and is not interchangeable with the ISO Standard C++ keyword. If your code might be compiled by using the [`/clr`](../build/reference/clr-common-language-runtime-compilation.md) compiler option, which targets managed code, then use `__nullptr` in any line of code where you must guarantee that the compiler uses the native C++ interpretation. For more information, see [`nullptr` (C++/CLI and C++/CX)](../extensions/nullptr-cpp-component-extensions.md).

## Remarks

Avoid using `NULL` or zero (`0`) as a null pointer constant; **`nullptr`** is less vulnerable to misuse and works better in most situations.  For example, given `func(std::pair<const char *, double>)`, then calling `func(std::make_pair(NULL, 3.14))` causes a compiler error.  The macro `NULL` expands to `0`, so that the call `std::make_pair(0, 3.14)` returns `std::pair<int, double>`, which isn't convertible to the `std::pair<const char *, double>` parameter type in `func`.  Calling `func(std::make_pair(nullptr, 3.14))` successfully compiles because `std::make_pair(nullptr, 3.14)` returns `std::pair<std::nullptr_t, double>`, which is convertible to `std::pair<const char *, double>`.

## See also

[Keywords](../cpp/keywords-cpp.md)<br/>
[`nullptr` (C++/CLI and C++/CX)](../extensions/nullptr-cpp-component-extensions.md)