DocumentationAnalyticsComponents Guide

How replays work

Last update: Fri Jan 09 2026 00:00:00 GMT+0000 (Coordinated Universal Time)

CREATED FOR:

  • Admin
AVAILABILITY
The functionality described in this section is only available to existing customers that already have a license for the functionality. The functionality is no longer offered as an additional add-on to existing or new customers.

Cross-Device Analytics makes two passes on data in a virtual report suite:

  • Live-stitching: CDA attempts to stitch each hit as it comes in. Net new devices to the report suite that have never logged in are typically not stitched at this level. Devices already recognized are stitched immediately.
  • Replay: Approximately once a week, CDA “replays” data based on unique identifiers it has learned. This stage is where new devices to the report suite become stitched.

Example table

The following tables illustrate how (Field-based stitching calculates the number of unique people:

Live-stitching

As soon as a hit is collected, CDA attempts to stitch it to known devices. Consider the following example, where Bob uses two devices.

Data as it appears the day it is collected:

Timestamp
ECID
eVar1 or CustomerID
Explanation of hit
People metric (cumulative) using field-based stitching
1
246
-
Bob on his desktop computer, unauthenticated
1 (246)
2
246
Bob
Bob logs in on his desktop
2 (246 and Bob)
3
3579
-
Bob on his mobile device, unauthenticated
3 (246, Bob, and 3579)
4
3579
Bob
Bob logs in on mobile
3 (246, Bob, and 3579)
5
246
-
Bob accesses your site on desktop again, unauthenticated
3 (246, Bob, and 3579)
6
246
Bob
Bob logs in again via desktop
3 (246, Bob, and 3579)
7
3579
-
Bob accesses your site again on mobile
3 (246, Bob, and 3579)
8
3579
Bob
Bob logs in again via mobile
3 (246, Bob, and 3579)

Both unauthenticated and authenticated hits on new devices are counted as separate people (temporarily).
Unauthenticated hits on recognized devices are live-stitched from that point forward. Attribution works as soon as the identifying custom variable ties to a device. In the example above, all hits except hits 1 and 3 are live-stitched (they all use the Bob identifier). Attribution works on hits 1 and 3 after replay stitching.

NOTE
Timestamped hits older than 12 hours are not stitched in the live flow. However, these hits are included in Replay stitching, as long as they fall in the replay lookback window.

Replay stitching

Replay occurs either daily or weekly, depending on how you requested CDA to be configured. During replay, CDA attempts to restate historical data within a defined lookback window:

  • Daily replay uses a 1-day lookback window
  • Weekly replay uses a 7-day lookback window.

If a device initially sends data while not authenticated and then logs in, CDA ties those unauthenticated hits to the correct person. The following table represents the same data as above, but shows different numbers based on replaying the data.

The same data after replay:

Timestamp
ECID
eVar1 or CustomerID
Explanation of hit
People metric (cumulative) using field-based stitching
1
246
-
Bob on his desktop computer, unauthenticated
1 (Bob)
2
246
Bob
Bob logs in on his desktop
1 (Bob)
3
3579
-
Bob on his mobile device, unauthenticated
1 (Bob)
4
3579
Bob
Bob logs in on mobile
1 (Bob)
5
246
-
Bob accesses your site on desktop again, unauthenticated
1 (Bob)
6
246
Bob
Bob logs in again via desktop
1 (Bob)
7
3579
-
Bob accesses your site again on mobile
1 (Bob)
8
3579
Bob
Bob logs in again via mobile
1 (Bob)
recommendation-more-help
46b8682c-fda6-4669-9355-1a44923e549e