cpp-httplib/docs-src/pages/en/cookbook/c02-json.md

title, order, status

title	order	status
C02. Send and Receive JSON	2	draft

cpp-httplib doesn't include a JSON parser. Use a library like nlohmann/json to build and parse JSON. The examples here use nlohmann/json.

Send JSON

httplib::Client cli("http://localhost:8080");

nlohmann::json j = {{"name", "Alice"}, {"age", 30}};
auto res = cli.Post("/api/users", j.dump(), "application/json");

Pass the JSON string as the second argument to Post() and the Content-Type as the third. The same pattern works with Put() and Patch().

Warning: If you omit the Content-Type (the third argument), the server may not recognize the body as JSON. Always specify "application/json".

Receive a JSON response

auto res = cli.Get("/api/users/1");
if (res && res->status == 200) {
  auto j = nlohmann::json::parse(res->body);
  std::cout << j["name"] << std::endl;
}

res->body is a std::string, so you can pass it straight to your JSON library.

Note: Servers sometimes return HTML on errors. Check the status code before parsing to be safe. Some APIs also require an Accept: application/json header. If you're calling a JSON API repeatedly, C03. Set default headers can save you some boilerplate.

For how to receive and return JSON on the server side, see S02. Receive JSON requests and return JSON responses.