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json/api/basic_json/std_hash.md
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2026-07-08 18:19:46 +00:00

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# <small>std::</small>hash<nlohmann::basic_json\>
```cpp
namespace std {
struct hash<nlohmann::basic_json>;
}
```
Return a hash value for a JSON object. The hash function tries to rely on `std::hash` where possible. Furthermore, the
type of the JSON value is taken into account to have different hash values for `#!json null`, `#!cpp 0`, `#!cpp 0U`, and
`#!cpp false`, etc.
## Examples
??? example
The example shows how to calculate hash values for different JSON values.
```cpp
--8<-- "examples/std_hash.cpp"
```
Output:
```json
--8<-- "examples/std_hash.output"
```
Note the output is platform-dependent.
## Version history
- Added in version 1.0.0.
- Extended for arbitrary basic_json types in version 3.10.5.