Eddystone is a Bluetooth Low Energy beacon profile released by Google in July 2015. The Apache 2.0-licensed, cross-platform, and versioned profile contains several frame types, including Eddystone-UID, Eddystone-URL, and Eddystone-TLM. Eddystone-URL is used by the Physical Web project, whereas Eddystone-UID is typically used by native apps on a user's device, including Google's first party apps such as Google Maps.
Background
The format was named after the Eddystone Lighthouse in the UK, motivated by the simplicity of a lighthouse-signal and its one-directional nature.
Technical details
Though similar to the iBeacon profile released by Apple in 2013, Eddystone can be implemented without restriction. Eddystone also contains a telemetry frame designed for reporting on a beacon's health, including, for example, battery level. Like other beacon technology, beacons with Eddystone can give devices a better indication of what objects and places are around them. Importantly, beacons do not generally accept connections from other devices, meaning that the beacon itself cannot record what devices are in its vicinity. In many cases, the simplicity of the beacon frame means that an app is required in order to interpret the beacon's signal. Nearby Messages is the API that can be used off of this protocol to receive data that is stored within beacons. Differing from iBeacon, Google beacon's use not only Bluetooth but also WiFi and near ultrasonic sounds to communicate between devices. Eddystone has 4 frame types.
Eddystone-UID broadcasts an identifying code that allows apps to retrieve information from app servers. These can be used for indoor location, identification of physical objects, and to interact with apps in any way the developer decides.
Eddystone-EID broadcasts an encrypted rotating identifier in order to increase the security of the protocol, but otherwise acts similarly to the UID frame
Eddystone-TLM broadcasts information about the beacon. This can include battery level, sensor data, or other relevant information to beacon administrators. It must be accompanied by another frame type to be usable as a beacon.
Eddystone-URL broadcasts a URL of at most 18 characters that redirects to a website that is secured using SSL. This beacon is the underpinning of the Physical Web.
*In android 4.4 or higher, it causes a notification to be displayed on the user's phone.
*On October 25th, 2018, Google announced that it will drop Nearby Notification based on Eddystone/Physical Web on December 6th, 2018.
Google beacon platform
In tandem with the Eddystone, Google launched the Google beacon platform. The platform includes the Proximity Beacon API designed to associate content with individual beacons. The Proximity Beacon API fronts a registry of beacons where extra information, useful to developers' applications, can be associated with individual beacon IDs. Several attachments can be associated with a single beacon. Attachments can be updated in real-time and can be retrieved by an app using the Nearby API in Android and the Nearby library for iOS.
Security
In 2018 the security of the platform came under scrutiny from privacy advocates with concerns over how the audio component of the beacon is recorded, stored and ultimately filtered to just the ultrasonic portion of the signal. Without proper informed consent, users may find their conversations are illegally being recorded by beacons using the Eddystone protocol in collaboration with the Nearby Messages API.
