ESP32 BLE Beacon Scanner Explained (2026)

Quick Summary :

This beginner guide explains a typical ESP32 BLE beacon scanner sketch: how scanning works, what RSSI means, how to detect iBeacon/Eddystone (or any BLE advertising packet), and how to filter by MAC address, UUID, or name. You’ll also learn the common gotchas (scan interval/window, duplicates, power use) and get a clean “working baseline” example you can paste into your own project.

1. What is a beacon scanner?

A “beacon” is just a device that broadcasts short BLE advertising packets (no pairing needed). Examples:

iBeacon tags (UUID/Major/Minor)
Eddystone beacons (URL/UID/TLM)
Phones, watches, trackers, BLE sensors that advertise
ESP32 boards advertising their name or service UUID

A beacon scanner is an ESP32 program that listens for those packets and prints out useful info like:

Device address (MAC)
Device name (if present)
RSSI (signal strength)
Manufacturer data (where iBeacon usually lives)
Service UUIDs (common for BLE sensors)

2. How BLE scanning works (in plain English)

BLE devices don’t “broadcast continuously”. They advertise in short bursts on three special channels:

A beacon sends an advertisement packet
Your ESP32 listens during a scan window
If it hears a packet, it triggers a callback (or stores the result)
Your code decides whether to print it, ignore it, or treat it as “found”

Two important settings control how often you’ll detect devices:

Scan interval: how often scanning cycles repeat
Scan window: how long you listen during each cycle

If the scan window is tiny, you’ll miss packets. If it’s huge, you’ll detect more but waste more power.

3. What RSSI means (and why it jumps)

RSSI is the received signal strength indicator, in dBm (usually negative numbers).

Typical interpretation indoors:

-30 to -55 dBm: very close (same room)
-55 to -70 dBm: close/medium (nearby rooms)
-70 to -90 dBm: far/weak (edge of range)

RSSI is noisy because of reflections, body blocking, walls, and antenna orientation. Expect it to bounce even when nothing moves.

If you want “presence detection”, use RSSI as a rough threshold with smoothing, not as a precise distance meter.

4. The “beacon scanner example” structure

Most ESP32 beacon scanner examples follow the same pattern:

Initialize BLE stack
Create a scanner object
Configure scan parameters (active scan, interval/window, duplicates)
Register a callback for discovered devices
Start scanning in a loop or on a timer
Print results or trigger actions

The only big difference between examples is the BLE library:

ESP32 BLE Arduino (older, heavier)
NimBLE-Arduino (lighter, faster, usually preferred today for scanning)

5. A clean beacon scanner example you can reuse

This is a simple “scan and print everything” example using NimBLE-Arduino style APIs. It prints address, name, RSSI, and raw manufacturer data when present.

#include <NimBLEDevice.h>class MyAdvertisedDeviceCallbacks : public NimBLEAdvertisedDeviceCallbacks {
  void onResult(NimBLEAdvertisedDevice* dev) override {
    Serial.print("ADDR: ");
    Serial.print(dev->getAddress().toString().c_str());    Serial.print("  RSSI: ");
    Serial.print(dev->getRSSI());    if (dev->haveName()) {
      Serial.print("  NAME: ");
      Serial.print(dev->getName().c_str());
    }    if (dev->haveManufacturerData()) {
      std::string mfg = dev->getManufacturerData();
      Serial.print("  MFG: ");
      for (size_t i = 0; i < mfg.size(); i++) {
        uint8_t b = (uint8_t)mfg[i];
        if (b < 16) Serial.print("0");
        Serial.print(b, HEX);
      }
    }    Serial.println();
  }
};NimBLEScan* pScan;void setup() {
  Serial.begin(115200);
  delay(300);  Serial.println("BLE Beacon Scanner starting...");  NimBLEDevice::init("");                 // no device name needed for scanning
  pScan = NimBLEDevice::getScan();  pScan->setAdvertisedDeviceCallbacks(new MyAdvertisedDeviceCallbacks(), true);  pScan->setActiveScan(true);             // request scan responses (more data, more power)
  pScan->setInterval(100);                // scan interval in ms
  pScan->setWindow(80);                   // scan window in ms (<= interval)
  pScan->setDuplicateFilter(true);        // reduce spam
}void loop() {
  // Scan for 5 seconds, then pause briefly
  pScan->start(5, false);
  delay(500);
}

What each setting does:

setActiveScan(true): ESP32 actively requests extra data (“scan response”). Helps reveal names/services but uses more power.
setInterval / setWindow: more window = better detection, more power.
setDuplicateFilter(true): you won’t print the same device constantly. Turn off if you want continuous RSSI tracking.

6. How to scan only for one beacon (MAC filter)

If you already know the beacon MAC address, filter in the callback:

const char* TARGET = "aa:bb:cc:dd:ee:ff";void onResult(NimBLEAdvertisedDevice* dev) override {
  if (dev->getAddress().toString() != TARGET) return;
  Serial.printf("FOUND %s RSSI=%d\n", TARGET, dev->getRSSI());
}

This is the fastest and most reliable filter.

7. How to detect iBeacon (UUID/Major/Minor idea)

iBeacon is normally embedded in manufacturer data (Apple’s company ID + iBeacon prefix + UUID + major/minor + tx power).

A beginner-friendly approach:

Print manufacturer data in hex (as in the example)
Confirm it matches an iBeacon pattern (you’ll see a consistent payload)
Then parse UUID/major/minor bytes once you know your tag format

Many “beacon scanner examples” stop at printing the manufacturer data because parsing differs by beacon type.

If you want a dedicated iBeacon parser section, tell me which tags you’re using (iBeacon vs Eddystone) and I’ll include a ready parser with UUID formatting.

8. “Why don’t I see my beacon?”

Common reasons:

You’re scanning BLE but the device is classic Bluetooth only
The beacon advertises rarely (long advertising interval)
Scan window is too small
You’re on “guest Wi-Fi” or network isolation (doesn’t matter for BLE itself, but matters if you expected phone apps to discover or to publish via MQTT)
The beacon randomizes its address (phones often do)
You’re too far or the beacon battery is dying

Quick fixes: