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2026-07-09 12:05:10 +00:00 · 2026-07-08 18:19:46 +00:00
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+# nlohmann::basic_json::to_msgpack
+
+```
+// (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.
+1. Writes the MessagePack serialization to an output adapter.
+
+The exact mapping and its limitations are described on a [dedicated page](https://json.nlohmann.me/features/binary_formats/messagepack/index.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
+1. (none)
+
+## Exception safety
+
+Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
+
+## 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.
+
+```
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+using namespace nlohmann::literals;
+
+int main()
+{
+    // create a JSON value
+    json j = R"({"compact": true, "schema": 0})"_json;
+
+    // serialize it to MessagePack
+    std::vector<std::uint8_t> v = json::to_msgpack(j);
+
+    // print the vector content
+    for (auto& byte : v)
+    {
+        std::cout << "0x" << std::hex << std::setw(2) << std::setfill('0') << (int)byte << " ";
+    }
+    std::cout << std::endl;
+}
+```
+
+Output:
+
+```
+0x82 0xa7 0x63 0x6f 0x6d 0x70 0x61 0x63 0x74 0xc3 0xa6 0x73 0x63 0x68 0x65 0x6d 0x61 0x00
+```
+
+## See also
+
+- [from_msgpack](https://json.nlohmann.me/api/basic_json/from_msgpack/index.md) create a JSON value from an input in MessagePack format
+- [to_cbor](https://json.nlohmann.me/api/basic_json/to_cbor/index.md) create a CBOR serialization of a JSON value
+- [to_bson](https://json.nlohmann.me/api/basic_json/to_bson/index.md) create a BSON serialization of a JSON value
+- [to_ubjson](https://json.nlohmann.me/api/basic_json/to_ubjson/index.md) create a UBJSON serialization of a JSON value
+- [to_bjdata](https://json.nlohmann.me/api/basic_json/to_bjdata/index.md) create a BJData serialization of a JSON value
+
+## Version history
+
+- Added in version 2.0.9.