A device ID is a stable identifier assigned to or derived from a specific device, used to recognise that device across sessions and visits. In web contexts where persistent storage may be cleared or unavailable, a fingerprint computed from hardware-bound signals can serve as a cookieless device ID that survives browser resets.
Traditional device IDs rely on persistent storage, such as a cookie or a local database entry, that the device writes once and reads on subsequent visits. These are simple and reliable but fragile: a user who clears storage or uses a private session loses the stored ID.
A fingerprint-based device ID replaces or supplements stored IDs with a value derived from the device itself. Because hardware characteristics change slowly, the derived ID remains consistent across sessions without depending on any writable storage.
In doorman-benny
doorman-benny exposes a stable, hardware-bound identifier via `getDeviceId()`, built from the same hardware signals that power `hardwareFingerprint` so the ID persists across browsers and private sessions.
getDeviceId (docs)Frequently asked questions
How is a fingerprint-based device ID different from a cookie?
A cookie is a value stored in the browser that the user can delete. A fingerprint-based device ID is computed from device characteristics each time it is needed, so clearing cookies or using incognito mode does not change it.
Is a fingerprint-based device ID unique per device?
It is designed to be highly distinctive, but it is a probabilistic identifier rather than a guaranteed globally unique one. Devices with very similar hardware configurations may occasionally produce matching values, so production systems combine it with other signals.
Does a device ID change when the user upgrades their browser?
Hardware-bound signals are largely independent of the browser version, so a hardware-based device ID is generally stable through browser updates. Engine-bound signals, used in a browser fingerprint rather than a device ID, are more sensitive to version changes.
