---
title: "Change detection (diff/delta)"
slug: "change-detection-diffdelta-1"
updated: 2025-03-12T18:25:12Z
published: 2025-03-12T18:25:12Z
canonical: "help.mozenda.com/change-detection-diffdelta-1"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://help.mozenda.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Change detection (diff/delta)

*Change detection* is a feature of [dexi.io](https://www.dexi.io/){target="_blank"} that can be used to determine when specific values of robot execution results change. Change detection can also be seen as *diff*ing or *delta* functionality.

[Output values](/v1/docs/what-should-i-know-about-input-and-output){target="_blank"} from the robot that you choose are compared from the current execution with the previous execution; in effect, providing a *sliding window* of changes. 

### Enable change detection
Contact us if you would like this feature enabled on your account. 

1. Search for **change detection** in Apps. 
2. Select **Contact Dexi**.

![Screenshot 2021-03-25 at 11.05.57.png](https://cdn.document360.io/03076343-9561-4857-8a4e-9f3bfed20ced/Images/Documentation/Screenshot%202021-03-25%20at%2011.05.57.png){height="" width=""}

### Configure change detection
Once the app is enabled, the feature is enabled for a [configuration](/v1/docs/how-can-i-create-a-run){target="_blank"} of a robot by checking the **Track changes?** checkbox:

![Screenshot 2020-02-06 at 13.33.01.png](https://cdn.document360.io/03076343-9561-4857-8a4e-9f3bfed20ced/Images/Documentation/Screenshot%202020-02-06%20at%2013.33.01.png){height="" width=""}

The **Key** fields define the fields that are used to determine the uniqueness of a row (i.e., when the values of the key fields match across the previous and the current execution). The values from the **Value** fields are then compared:
* If values are new, the row is marked as **Created**.
* If values are unchanged, the row is marked as **Existed**.
* If values have changed, the row is marked as **Changed**.
* If values were deleted, the row is marked as **Deleted**.

A field cannot be selected as both a key and value field and currently, only non-file, non-object, and non-array/list fields (i.e., **simple** fields), are supported for both key and value fields.

### Results with change detection
The change status is added to the results as a separate field, *Change* — called **@change** when results are exported or when using change detection from triggers.

Example showing only *Changed* rows:
![Screenshot 2020-02-06 at 13.46.30.png](https://cdn.document360.io/03076343-9561-4857-8a4e-9f3bfed20ced/Images/Documentation/Screenshot%202020-02-06%20at%2013.46.30.png){height="" width=""}

If any rows were deleted, they are shown on the **Deleted results** tab.

The **Old value prefix** controls the name of the *old* fields, i.e., the fields of the rows of the previous execution. In the example below, the prefix **previous-** has been entered:

![Screenshot 2020-02-06 at 13.50.31.png](https://cdn.document360.io/03076343-9561-4857-8a4e-9f3bfed20ced/Images/Documentation/Screenshot%202020-02-06%20at%2013.50.31.png){height="" width=""}

If left blank, the prefix **old-** is used.

:::(Info) (**Tip!**)
This part of Dexi doesn't have auto-save. Remember to save when you are changing any part of the change detection configuration (or any other part of the robot configuration for that matter).
:::

### Change detection with triggers
The **old value** fields and the **@change** field are available from [triggers](/v1/docs/what-are-triggers){target="_blank"} and can be mapped just like the *normal* fields from the result rows:

![Screenshot 2020-02-06 at 13.58.14.png](https://cdn.document360.io/03076343-9561-4857-8a4e-9f3bfed20ced/Images/Documentation/Screenshot%202020-02-06%20at%2013.58.14%281%29.png){height="" width=""}

### See also:

* [Datasets with deduplication and record linkage](/v1/docs/using-data-sets){target="_blank"}