ESP32 HTTP POST with JSON Body Fails

In this tutorial, you'll learn about ESP32 HTTP POST with JSON Body Fails. We cover key concepts, practical examples, and best practices.

The Problem

ESP32 sends POST with JSON body but server returns 400 Bad Request or ignores data.

Quick Fix

Wrong

HTTPClient http;
http.begin("http://api.example.com/data");
http.POST("{\'temp\':22.5}");

Server returns 400 Bad Request or 415 Unsupported Media Type.

Right

HTTPClient http;
http.begin("http://api.example.com/data");
http.addHeader("Content-Type", "application/json");
String json = "{\'temp\':22.5,\'humidity\':60}";
int code = http.POST(json);
if (code == 200 || code == 201) {
  Serial.printf("POST success: %s", http.getString().c_str());
}
http.end();

POST success: {"id": 123, "status": "created"}

Prevention

Set Content-Type: application/json header before POST. Escape double quotes properly. Check 200/201 for success. Use ArduinoJson library. Validate JSON before sending.

DodaTech engineers apply these same patterns across Doda Browser, DodaZIP, and Durga Antivirus Pro for production IoT reliability.

FAQ