Hackle ID

Accurately identifying unique users is critical for user data analysis. Depending on the nature of your service, users may access the service while logged in or logged out, and a single user may use multiple devices.

To accurately identify unique users, Hackle uses a combination of User ID, Device ID, and Hackle ID.

This document explains how the Hackle ID works.

Hackle ID

Let's look at the scenarios that can occur when assigning Hackle IDs. Each case describes how Hackle IDs are created or reused using User ID and Device ID.

Only logged-out users

When there is no User ID (i.e., the user is not logged in), a new Hackle ID is created and assigned for each new Device ID.

Device ID	User ID	Hackle ID
A	null	1
B	null	2
A	null	1
A	null	1
C	null	3
B	null	2
C	null	3

• The first event occurred on device A, and since there was no prior record for this device, a new Hackle ID of 1 is assigned.

• The second event occurred on device B, and since there was no prior record for this device either, Hackle ID 2 is assigned.

• The third event occurred on device A, so the already-assigned Hackle ID 1 is reused.

User who was logged out and then logs in

When there is no User ID, events from the same Device ID without a User ID are assumed to belong to the same user. In this case, the same Hackle ID is assigned.

Device ID	User ID	Hackle ID
D	null	4
D	null	4
D	Jay	4

• The first two events occurred on device D without a User ID, and Hackle ID 4 was assigned.

• The third event is the first event from device D that includes a User ID. The same Hackle ID as the prior events is assigned to this User ID. As a result, all three events are recorded as having been triggered by Jay.

A logged-in user using multiple devices

When assigning a Hackle ID, User ID takes priority over Device ID.

Device ID	User ID	Hackle ID
E	Lyle	5
F	Lyle	5
G	Lyle	5

• Lyle triggered an event on device E and was assigned Hackle ID 5.

• When the User ID is Lyle, Hackle ID 5 is assigned regardless of the Device ID.

Multiple users sharing one device

After Device ID and User ID are assigned to the same Hackle ID, if an event occurs on the same device without a User ID, it is assumed to have been triggered by the last user, and that user's Hackle ID is assigned.

Device ID	User ID	Hackle ID
H	Mark	6
H	null	6
H	Alley	7
H	null	7
H	null	7

• Mark triggered an event on device H and was assigned Hackle ID 6.

• The next event was sent without a User ID, but since Mark was the last user on this device, Hackle ID 6 is assigned.

• The third event was triggered by Alley on device H, and Alley's corresponding Hackle ID 7 is assigned.

• The next two events have no User ID, but they are assumed to have been triggered by Alley, the last user on device H.

A user switching devices and logging in

Device ID	User ID	Hackle ID
Y	Jamie	8
Z	null	9
Z	Jamie	8
Z	null	8

• Jamie triggered an event on device Y and was assigned Hackle ID 8.

• An event occurred on device Z without a User ID, and Hackle ID 9 was assigned.

• Jamie logged in on device Z, and an event with a User ID was triggered, assigning Jamie's Hackle ID 8.

• Subsequent events on device Z without a User ID are assigned Hackle ID 8 since Jamie was the last user.