Whoop 4.0 Reverse Engineering
A comprehensive guide to understanding and controlling the Whoop 4.0 fitness tracker through Bluetooth Low Energy protocol analysis
What is this guide?
This documentation provides a complete walkthrough of reverse engineering the Whoop 4.0 fitness tracker’s Bluetooth Low Energy (BLE) communication protocol. By understanding how the device communicates with its official app, you can build custom integrations, automate device functions, and gain independent control over your hardware.Why reverse engineer Whoop?
The Whoop 4.0 represents an extreme case of subscription-driven hardware. Unlike traditional fitness trackers, Whoop doesn’t sell the device directly—instead, they sell memberships and provide the hardware “for free.” To use the device you already own, you must maintain an active subscription. This guide empowers you to:- Break free from subscription lock-in — Use your hardware without ongoing fees
- Customize functionality — Set multiple daily alarms, not just one
- Access your data — Retrieve sensor readings on your own terms
- Build custom integrations — Connect Whoop to your own applications
- Learn BLE reverse engineering — Develop skills applicable to any IoT device
What you’ll learn
Protocol Analysis
Discover BLE services, characteristics, and command structures
Packet Structure
Decode packet headers, checksums, and data payloads
Device Control
Send commands to control alarms, tracking, and broadcasting
Data Retrieval
Sync heart rate, activity, and health monitoring data
Device capabilities
The Whoop 4.0 includes several sensors, though not all are accessible without the subscription service:- Heart rate — Continuous measurement (accessible via standard BLE Heart Rate Service)
- Blood oxygen — Measured once daily during sleep (requires protocol reverse engineering)
- Temperature — Measured once daily during sleep (requires protocol reverse engineering)
- Vibration motor — Used for alarms and notifications
- Data storage — On-device storage for sensor readings
Methodology overview
This guide follows a systematic reverse engineering process:- Reconnaissance — Identify BLE services and characteristics using scanners
- Traffic capture — Monitor communication between the official app and device using Wireshark and ADB
- Packet analysis — Decode packet structures, checksums, and command formats
- Command injection — Send custom commands to control device functions
- Data extraction — Retrieve stored sensor data through sync protocols
Tools you’ll need
Wireshark
Capture and analyze Bluetooth packets in real-time
ADB
Extract Bluetooth HCI logs from Android devices
Python Libraries
Use pygatt, bleak, and gatttool for BLE communication
BLE Scanner
Discover services and characteristics on the device
Get started
Ready to take control of your Whoop 4.0? Start with the prerequisites guide to set up your environment.Prerequisites
Set up the tools and environment needed for BLE reverse engineering
This guide is for educational purposes. Reverse engineering may void your warranty and violate terms of service. Proceed at your own risk.