The Fast, Fluent and Zero-Heap REST Client for ESP32 Microcontrollers
Stream HTTP and REST responses directly into native C/C++ variables. Eliminate intermediate buffers, reduce RAM usage by 99.9%, and accelerate requests with native TLS Keep-Alive.
Standard HTTPClient + ArduinoJson
15 lines of boilerplate & heap allocation
HTTPClient http;
http.begin("http://api/sensor");
int httpCode = http.GET();
if (httpCode == HTTP_CODE_OK) {
String payload = http.getString();
DynamicJsonDocument doc(1024);
deserializeJson(doc, payload);
float temp = doc["temperature"];
}
http.end();ESP32-HTTP-Client
1 clean line & 0 intermediate buffers
float temp = 0.0f;
client.get("/sensor")
.getBody("temperature", &temp);99.9% Less RAM
15 bytes vs 58.2 KB heap per request
12x Faster
Native Keep-Alive & TLS connection reuse
~0.0 KB Heap Alloc
Zero heap fragmentation risk
90% Less Code
Direct variable injection in 1 line
Engineered for Constrained Embedded Systems
Tested on ESP32 across 100 consecutive HTTPS requests fetching JSON payloads from public REST APIs.
ESP32-WROOM-32 @ 240MHz, Arduino Core v3.x, HTTPS with TLS encryption
| Metric | Standard (HTTPClient + ArduinoJson) | ESP32-HTTP-Client | Advantage |
|---|---|---|---|
| Heap Allocation per Request | ~58.2 KB (Buffers + JSON Doc) | ~0.0 KB (15 bytes metadata) | 99.9% Less RAM |
| Average Execution Time | ~750 ms (Handshake per call) | ~59 ms (Native Keep-Alive) | 12x Faster Execution |
| Average RAM Footprint | 34.2% total heap used | 24.3% total heap used | 29% Lower Total RAM |
| Absolute Min. Free Heap | 114.3 KB | 128.6 KB | +14.3 KB Margin |
| Code Complexity | 15+ lines (String, doc, deserialize) | 1 chained statement (.get().getBody()) | Clean & Maintainable |
| Memory Safety | Prone to heap fragmentation | Direct stream-to-variable write | Zero Fragmentation |
Why is it 12x faster with 0 heap?
Standard Arduino libraries close sockets after each call, incurring heavy TLS handshakes (300-800ms) and buffering complete responses into RAM. ESP32-HTTP-Client reuses the underlying TLS session and streams bytes directly into target memory addresses.
Built for Embedded & Production IoT
From simple sensor telemetry to complex API integrations, build reliable firmware without memory fragmentation.
Direct Variable Binding
No intermediate JSON document objects. Directly bind JSON keys into native C/C++ primitive types or structs.
client.get("/sensor").getBody("temperature", &tempFloat);Streaming Parser
Parses incoming network packets as they arrive from the TCP socket. The full payload is never stored in RAM.
client.get("/large-payload").getBody("targetField", &result);Fluent C++ Interface
Chained method calls for intuitive request construction. Append query parameters, path placeholders, headers, and bodies.
client.get("/users/{id}").path("id", 42).query("verbose", true);Full REST HTTP Verbs
Support for GET, POST, PUT, PATCH, and DELETE methods with automatic headers, status code inspection, and error handling.
client.post("/telemetry").body("val", 98.6).getBody("id", &id);Dot Notation Navigation
Traverse nested JSON payloads and arrays using clean dot syntax without writing custom parsers.
client.get("/users").getBody("0.company.address.city", cityBuffer, 32);Struct Serialization
Serialize and deserialize custom C++ structs directly to and from JSON payloads with zero dynamic allocations.
MySensorData data; client.get("/state").getStruct(&data);JSON to C++ Binding Generator
Paste any JSON payload or select a preset below to generate ESP32-HTTP-Client C++ code.
#include <ESP32HTTPClient.h>
ESP32HTTPClient client("api.example.com");
void fetchData() {
float temperature = 0.0f;
float humidity = 0.0f;
int sensor_id = 0;
char status[64] = {0};
client.get("/data")
.getBody("temperature", &temperature)
.getBody("humidity", &humidity)
.getBody("sensor_id", &sensor_id)
.getBody("status", status, sizeof(status));
}Variables are declared on the stack and populated directly via .getBody() without allocating dynamic memory.
Get Started in Minutes
Install via your preferred package manager and execute your first zero-heap HTTP request.
1. Install Library
Search for "ESP32-HTTP-Client" in Arduino Library Manager or add the dependency to platformio.ini.
2. Include & Initialize
Instantiate the client with your base API domain or local endpoint.
3. Execute Request
Chain your query, path, and body bindings in a single line.
[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
lib_deps =
PedroFnseca/ESP32-HTTP-Client @ ^1.5.1Frequently Asked Questions
Direct technical answers regarding performance, memory management, and compatibility.
Traditional HTTPClient + ArduinoJson buffers the complete HTTP response in a String before deserialization, consuming 30KB–60KB+ of heap per request and causing fragmentation. ESP32-HTTP-Client streams bytes directly into target variables with zero intermediate document allocation, using only ~15 bytes of heap.
Build Reliable ESP32 Applications
Streamlined REST client with clean syntax, fast execution, and zero heap fragmentation.