# <small>nlohmann::basic_json::</small>to_msgpack

```cpp
// (1)
static std::vector<std::uint8_t> to_msgpack(const basic_json& j);

// (2)
static void to_msgpack(const basic_json& j, detail::output_adapter<std::uint8_t> o);
static void to_msgpack(const basic_json& j, detail::output_adapter<char> o);
```

Serializes a given JSON value `j` to a byte vector using the MessagePack serialization format. MessagePack is a binary
serialization format that aims to be more compact than JSON itself, yet more efficient to parse.

1. Returns a byte vector containing the MessagePack serialization.
2. Writes the MessagePack serialization to an output adapter.

The exact mapping and its limitations are described on a [dedicated page](../../features/binary_formats/messagepack.md).

## Parameters

`j` (in)
:   JSON value to serialize

`o` (in)
:   output adapter to write serialization to

## Return value

1. MessagePack serialization as a byte vector
2. (none)

## Exception safety

Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

## Exceptions

- Throws [`out_of_range.412`](../../home/exceptions.md#jsonexceptionout_of_range412) if the length of a string, binary
  value, array, or object exceeds 4294967295, the maximum MessagePack can store; example:
  `"MessagePack length 4294967296 exceeds maximum of 4294967295"`
- Throws [`out_of_range.415`](../../home/exceptions.md#jsonexceptionout_of_range415) if the subtype of a binary value
  exceeds 255, the maximum of the MessagePack ext type; example:
  `"subtype 70000 is too large for the MessagePack ext type (max 255)"`

## Complexity

Linear in the size of the JSON value `j`.

## Examples

??? example

    The example shows the serialization of a JSON value to a byte vector in MessagePack format.
     
    ```cpp
    --8<-- "examples/to_msgpack.cpp"
    ```
    
    Output:
    
    ```json
    --8<-- "examples/to_msgpack.output"
    ```

## See also

- [from_msgpack](from_msgpack.md) create a JSON value from an input in MessagePack format
- [to_cbor](to_cbor.md) create a CBOR serialization of a JSON value
- [to_bson](to_bson.md) create a BSON serialization of a JSON value
- [to_ubjson](to_ubjson.md) create a UBJSON serialization of a JSON value
- [to_bjdata](to_bjdata.md) create a BJData serialization of a JSON value
- [to_bon8](to_bon8.md) create a BON8 serialization of a JSON value

## Version history

- Added in version 2.0.9.
- Throws `out_of_range.412` and `out_of_range.415` since version 3.13.0.