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<span class=kc>true</span>
<span class=kc>true</span>
<span class=kc>true</span>
</code></pre></div> </details> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 1.0.0.</li> <li>Added unsigned integer type in version 2.0.0.</li> <li>Added binary type in version 3.8.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="July 4, 2026 09:13:25 UTC">July 4, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 1.0.0.</li> <li>Added unsigned integer type in version 2.0.0.</li> <li>Added binary type in version 3.8.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="July 8, 2026 18:18:24 UTC">July 8, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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api/basic_json/value_t/index.md
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@@ -0,0 +1,105 @@
# nlohmann::basic_json::value_t
```
enum class value_t : std::uint8_t {
null,
object,
array,
string,
boolean,
number_integer,
number_unsigned,
number_float,
binary,
discarded
};
```
This enumeration collects the different JSON types. It is internally used to distinguish the stored values, and the functions [`is_null`](https://json.nlohmann.me/api/basic_json/is_null/index.md), [`is_object`](https://json.nlohmann.me/api/basic_json/is_object/index.md), [`is_array`](https://json.nlohmann.me/api/basic_json/is_array/index.md), [`is_string`](https://json.nlohmann.me/api/basic_json/is_string/index.md), [`is_boolean`](https://json.nlohmann.me/api/basic_json/is_boolean/index.md), [`is_number`](https://json.nlohmann.me/api/basic_json/is_number/index.md) (with [`is_number_integer`](https://json.nlohmann.me/api/basic_json/is_number_integer/index.md), [`is_number_unsigned`](https://json.nlohmann.me/api/basic_json/is_number_unsigned/index.md), and [`is_number_float`](https://json.nlohmann.me/api/basic_json/is_number_float/index.md)), [`is_discarded`](https://json.nlohmann.me/api/basic_json/is_discarded/index.md), [`is_binary`](https://json.nlohmann.me/api/basic_json/is_binary/index.md), [`is_primitive`](https://json.nlohmann.me/api/basic_json/is_primitive/index.md), and [`is_structured`](https://json.nlohmann.me/api/basic_json/is_structured/index.md) rely on it.
## Notes
Ordering
The order of types is as follows:
1. `null`
1. `boolean`
1. `number_integer`, `number_unsigned`, `number_float`
1. `object`
1. `array`
1. `string`
1. `binary`
`discarded` is unordered.
Types of numbers
There are three enumerators for numbers (`number_integer`, `number_unsigned`, and `number_float`) to distinguish between different types of numbers:
- [`number_unsigned_t`](https://json.nlohmann.me/api/basic_json/number_unsigned_t/index.md) for unsigned integers
- [`number_integer_t`](https://json.nlohmann.me/api/basic_json/number_integer_t/index.md) for signed integers
- [`number_float_t`](https://json.nlohmann.me/api/basic_json/number_float_t/index.md) for floating-point numbers or to approximate integers which do not fit into the limits of their respective type
Comparison operators
`operator<` and `operator<=>` (since C++20) are overloaded and compare according to the ordering described above. Until C++20 all other relational and equality operators yield results according to the integer value of each enumerator. Since C++20 some compilers consider the *rewritten candidates* generated from `operator<=>` during overload resolution, while others do not. For predictable and portable behavior use:
- `operator<` or `operator<=>` when wanting to compare according to the order described above
- `operator==` or `operator!=` when wanting to compare according to each enumerators integer value
## Examples
Example
The following code how `type()` queries the `value_t` for all JSON types.
```
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
// create JSON values
json j_null;
json j_boolean = true;
json j_number_integer = -17;
json j_number_unsigned = 42u;
json j_number_float = 23.42;
json j_object = {{"one", 1}, {"two", 2}};
json j_array = {1, 2, 4, 8, 16};
json j_string = "Hello, world";
// call type()
std::cout << std::boolalpha;
std::cout << (j_null.type() == json::value_t::null) << '\n';
std::cout << (j_boolean.type() == json::value_t::boolean) << '\n';
std::cout << (j_number_integer.type() == json::value_t::number_integer) << '\n';
std::cout << (j_number_unsigned.type() == json::value_t::number_unsigned) << '\n';
std::cout << (j_number_float.type() == json::value_t::number_float) << '\n';
std::cout << (j_object.type() == json::value_t::object) << '\n';
std::cout << (j_array.type() == json::value_t::array) << '\n';
std::cout << (j_string.type() == json::value_t::string) << '\n';
}
```
Output:
```
true
true
true
true
true
true
true
true
```
## Version history
- Added in version 1.0.0.
- Added unsigned integer type in version 2.0.0.
- Added binary type in version 3.8.0.