How to Send DHT11/DHT22 Data from an ESP8266 to Firebase

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You can send temperature and humidity from a DHT11 or DHT22 to Firebase Realtime Database using an ESP8266, Wi-Fi, and an HTTPS REST request. The complete path is:

DHT11/DHT22 → ESP8266 → Wi-Fi → HTTPS PUT → Firebase Realtime Database

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This guide uses Firebase Realtime Database—not Firestore—and uses its REST API as the primary approach. REST makes the URL, JSON payload, authentication, and HTTP response visible, which makes the project easier to debug. It also avoids relying on older Firebase Arduino libraries that are now deprecated.

What you will build

The ESP8266 will read a DHT sensor and write an object like this to Firebase:

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{
  "temperatureC": 23.7,
  "humidity": 48.2,
  "sampledAt": 1787059200
}

The data will be stored at:

/sensors/esp8266-01/latest

Its REST endpoint is the Firebase database URL followed by the path and .json:

https://YOUR_DATABASE_URL/sensors/esp8266-01/latest.json

Firebase documents PUT for replacing data at a known path, PATCH for updating selected child fields, and POST for creating a unique child key. See the Firebase REST documentation and REST write-method documentation.

Parts and software

• NodeMCU ESP8266, Wemos D1 mini, or ESP-01 with suitable USB-to-serial programming hardware
• DHT11 or DHT22 sensor
• Jumper wires
• Stable 3.3 V power
• A 2.4 GHz Wi-Fi network with internet access
• Arduino IDE

Install the ESP8266 board package in Arduino IDE, then install these libraries through Library Manager:

• DHT sensor library by Adafruit
• Adafruit Unified Sensor, if requested by the installed DHT library

Use DHT11 or DHT22 to match the physical sensor. Do not select DHT22 simply because it is common in older examples.

Wire the DHT sensor

Board labels such as D2 are aliases, not universal GPIO names. Confirm the mapping for your board. Avoid boot-strap pins unless you understand the ESP8266 boot requirements. A bare DHT sensor may need a pull-up resistor on its data line; many breakout modules already include one.

The ESP8266 is a 3.3 V device. Do not apply 5 V to an ESP8266 GPIO.

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Adafruit’s ESP8266 DHT example also uses the ESP8266 Wi-Fi library, a DHT library, and a conservative interval between readings.

Create a Firebase Realtime Database

1. Open the Firebase console and create or open a project.
2. Open Databases & Storage.
3. Select Realtime Database.
4. Choose Create database and select the database location.
5. Copy the database URL shown for your instance.

Firebase database URLs are not always identical. Depending on the instance location, the URL may resemble:

https://DATABASE_NAME.firebaseio.com

or:

https://DATABASE_NAME.REGION.firebasedatabase.app

Use the URL Firebase gives your project; do not construct one by guessing the region. Firebase’s current Realtime Database REST setup guide documents the console flow and URL formats.

Choose a data structure

For a device named esp8266-01, use this structure:

sensors
└── esp8266-01
    ├── latest
    │   ├── temperatureC
    │   ├── humidity
    │   └── sampledAt
    └── readings
        └── generated-reading-id

Use PUT for latest. Each upload replaces the previous current reading, so the path remains small.

Use POST for readings when you want a history. Firebase generates a unique child key for each request. Historical data grows continuously, so add a retention or archive strategy for a real deployment.

Test the sensor before adding Firebase

First confirm that the DHT sensor itself works. Upload a simple DHT example, print the values to Serial Monitor at 115200 baud, and check that the result is numeric. A failed DHT read commonly appears as NaN.

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Likely causes of NaN include the wrong sensor type, an incorrect GPIO, a missing pull-up resistor, loose wiring, unstable power, or readings taken too frequently. A roughly two-second interval is a practical starting point, not a universal requirement for every DHT module.

Authentication and security

Firebase REST requests can use OAuth 2 access tokens, Firebase ID tokens, or legacy database secrets. For a new project, do not put a Firebase service-account private key in ESP8266 firmware. Anyone who extracts the firmware may be able to recover credentials.

For a temporary connectivity test, permissive rules can help determine whether Wi-Fi, JSON, and the endpoint work. However, test-mode rules may allow anyone to read or overwrite data. They must not be treated as a production configuration. Review Firebase’s REST authentication documentation before deploying.

The example below expects a Firebase ID token in FIREBASE_ID_TOKEN. A Firebase ID token expires after a short period, so production firmware must refresh or reacquire it. A permanent hard-coded token is not a complete device-identity design.

For a small demonstration, you can temporarily use an endpoint that accepts the token. For a production device, choose one of these architectures:

1. Authenticated device user: the ESP8266 authenticates as a restricted Firebase user and sends a current ID token.
2. Backend ingestion: the ESP8266 sends data to your HTTPS endpoint, and a server uses server-side Firebase credentials to write to Realtime Database.
3. Restricted direct device access: use only when the project’s threat model accepts the risk of credentials being extracted from firmware.

Complete ESP8266 REST sketch

Select the correct DHTTYPE, enter your Wi-Fi credentials, database URL, and current authentication token, then upload the sketch.

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#include <ESP8266WiFi.h>
#include <WiFiClientSecureBearSSL.h>
#include <ESP8266HTTPClient.h>
#include <DHT.h>

#define DHTPIN 4
#define DHTTYPE DHT22       // Change to DHT11 when appropriate

const char* WIFI_SSID = "YOUR_WIFI_SSID";
const char* WIFI_PASSWORD = "YOUR_WIFI_PASSWORD";

const char* FIREBASE_URL =
  "https://YOUR_DATABASE_URL/sensors/esp8266-01/latest.json";

const char* FIREBASE_ID_TOKEN = "YOUR_ID_TOKEN";

DHT dht(DHTPIN, DHTTYPE);

unsigned long lastSample = 0;
const unsigned long sampleInterval = 2000;

void connectWiFi() {
  if (WiFi.status() == WL_CONNECTED) return;

  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);

  Serial.print("Connecting to Wi-Fi");
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println();
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
}

void setup() {
  Serial.begin(115200);
  dht.begin();
  connectWiFi();
}

void loop() {
  if (millis() - lastSample < sampleInterval) {
    delay(10);
    return;
  }

  lastSample = millis();
  connectWiFi();

  float humidity = dht.readHumidity();
  float temperatureC = dht.readTemperature();

  if (isnan(humidity) || isnan(temperatureC)) {
    Serial.println("DHT read failed");
    return;
  }

  String payload = "{";
  payload += ""temperatureC":";
  payload += String(temperatureC, 2);
  payload += ","humidity":";
  payload += String(humidity, 2);
  payload += "}";

  BearSSL::WiFiClientSecure client;

  // Diagnostic shortcut only; it disables certificate verification.
  client.setInsecure();

  HTTPClient https;

  if (!https.begin(client, FIREBASE_URL)) {
    Serial.println("HTTPS connection failed");
    return;
  }

  https.addHeader("Content-Type", "application/json");
  https.addHeader(
    "Authorization",
    String("Bearer ") + FIREBASE_ID_TOKEN
  );

  int httpCode = https.PUT(payload);

  Serial.print("HTTP status: ");
  Serial.println(httpCode);

  if (httpCode > 0) {
    Serial.println(https.getString());
  } else {
    Serial.println(https.errorToString(httpCode));
  }

  https.end();
}

What the sketch does

1. Connects to a 2.4 GHz Wi-Fi network.
2. Reads temperature and humidity from the DHT sensor.
3. Rejects invalid readings instead of uploading NaN.
4. Builds numeric JSON values. The values are not enclosed in quotes, so Firebase stores them as numbers.
5. Uses an HTTPS client to send a PUT request.
6. Prints the HTTP status and Firebase response to Serial Monitor.

Important TLS limitation

client.setInsecure() disables certificate verification. It can help diagnose connectivity, but it does not provide full protection against an impersonated server. Production firmware should validate the Firebase server certificate using a trusted root certificate or another supported ESP8266 TLS configuration.

Firebase REST requires HTTPS; ordinary unencrypted HTTP is not the correct endpoint protocol. See the Firebase Realtime Database REST reference.

Verify the upload in Firebase

Open the Firebase console, select Realtime Database, and navigate to:

sensors/esp8266-01/latest

You should see values similar to:

{
  "humidity": 48.2,
  "temperatureC": 23.7
}

The exact readings depend on the sensor, wiring, environment, and calibration. DHT sensors are suitable for basic hobby projects, not automatically for laboratory-grade measurement.

Useful REST variations

Append a historical reading with POST

Send the same JSON object to:

https://YOUR_DATABASE_URL/sensors/esp8266-01/readings.json

Using POST creates a generated child key. This is appropriate for append-only history.

Update selected fields with PATCH

A PATCH request can update only selected child values, such as device status or uptime, without replacing the complete object.

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• 𝐇𝐢𝐠𝐡-𝐐𝐮𝐚𝐥𝐢𝐭𝐲 𝐄𝐥𝐞𝐜𝐭𝐫𝐨𝐧𝐢𝐜𝐬 𝐂𝐨𝐦𝐩𝐨𝐧𝐞𝐧𝐭𝐬: Our temperature humidity monitor sensor module are made with top-of-the-line electronics components, ensuring reliable and long-lasting performance
• 𝐐𝐮𝐚𝐥𝐢𝐭𝐲 & 𝐏𝐫𝐞𝐜𝐢𝐬𝐢𝐨𝐧: This digital sensor module offers accurate environmental readings, measuring humidity from 0% to 100% RH with a precision of ±2% RH, and temperature from -40°C to 80°C with an accuracy of ±0.5°C. (Compatible with DHT22 specifications.)
• 𝐑𝐞𝐥𝐢𝐚𝐛𝐥𝐞 & 𝐄𝐚𝐬𝐲 𝐈𝐧𝐭𝐞𝐠𝐫𝐚𝐭𝐢𝐨𝐧: Equipped with advanced digital signal output and a high-performance 8-bit microcontroller, this digital sensor module ensures long-term stability, quick response times, and strong anti-interference capabilities. Its single-wire wiring scheme simplifies integration into various applications. We recommend using AI tools to assist with programming
• 𝐂𝐨𝐦𝐩𝐚𝐜𝐭 & 𝐔𝐬𝐞𝐫-𝐅𝐫𝐢𝐞𝐧𝐝𝐥𝐲 𝐃𝐞𝐬𝐢𝐠𝐧: This digital sensor module features a compact size of 38mm (L) x 15mm (W) x 10mm (H) and a lightweight design at approximately 6.4g. Operate Voltage: DC 3~5.5V. High sensitive temperature humidity sensor,single-bus digital signal output, bidirectional serial data.
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Delete a path

A DELETE request removes the data at the selected path. Use this carefully, especially when deleting historical readings.

Example Security Rules

This is an illustrative authenticated-user pattern:

{
  "rules": {
    "sensors": {
      "$deviceId": {
        ".read": "auth != null",
        ".write": "auth != null && auth.uid === $deviceId"
      }
    }
  }
}

It assumes that the Firebase Authentication UID exactly matches the device ID. Adapt it to your identity model. Decide whether devices should be allowed to read data, whether historical records should be immutable, and whether rules should validate numeric ranges and timestamps.

Rules protect Firebase resources; they cannot prevent an attacker from extracting credentials from compromised firmware. For multiple devices, device provisioning and backend-mediated ingestion are safer designs than sharing one credential.

Troubleshooting

Improve reliability for a real device

• Use millis() rather than long blocking delays when the ESP8266 must perform other tasks.
• Add a Wi-Fi connection timeout so the device cannot block forever.
• Retry temporary network failures with increasing delays rather than reconnecting in a tight loop.
• Send only valid sensor values.
• Do not print Wi-Fi passwords, tokens, or other credentials to Serial Monitor.
• Use certificate verification in production.
• Remember that Firebase ID tokens expire and must be refreshed.
• Buffer readings locally only when data loss matters; repeated flash writes can contribute to flash wear.
• Consider a backend ingestion service when deploying multiple devices or handling untrusted networks.

Should you use FirebaseClient instead?

Direct REST is the clearest option for this small tutorial, but a maintained Arduino library can be useful when the project needs Firebase Authentication, asynchronous operations, or several Firebase services.

The older FirebaseArduino, Firebase-ESP8266, and Firebase-ESP-Client examples found in many tutorials should not be treated as the preferred starting point for a new project. The Firebase-ESP-Client repository is marked deprecated and points users toward FirebaseClient. The newer library supports ESP8266 and Realtime Database, is available through Arduino IDE’s Library Manager, and has a different API from older examples. Its bare-minimum Realtime Database example is the appropriate reference for that route.

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Possible extensions

• Store historical values under /readings with POST.
• Add uptime, Wi-Fi signal strength, firmware version, and device status.
• Build a web dashboard that reads the Realtime Database.
• Use Cloud Functions or another backend for alerts and processing.
• Add OTA firmware updates.
• Buffer a small number of readings during temporary Wi-Fi outages.
• Use a device-specific path such as /sensors/$deviceId for multiple ESP8266 boards.

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