# Changed Elements

The Changed Elements API provides consumers with the elements that have changed in an iModel between two changesets. This API has two operations:

1. Enable Change Tracking
2. Get Comparison

Before obtaining a comparison, it is necessary to enable change tracking of an iModel. This means that the API will be listening to any new `Named Versions` that are created on the iModel. When that happens, the API will process the new changes and store a summary of all the elements that have changed.

After tracking is enabled and the iModel is processed, the comparison endpoint may be used to query for a summary of changed elements between any two given `ChangeSets`.

changed-elements

Project Delivery

---

Enables or disables change tracking for an iModel. This operation requires you to pass the enable value, iModel Id and project Id in the body of the request as a JSON object.

Once enabled, whenever a new named version is created in the iModel, the changesets will be processed to find all changed elements. This data can then be requested by using the Get Comparison operation.

### Authentication

Requires `Authorization` header with valid Bearer token for scope `changedelements:modify`.

For more documentation on authorization and how to get access token visit [OAUTH2 Authorization](https://developer.bentley.com/apis/overview/authorization/) page.

---

enable-change-tracking

The body should contain a JSON object with the enable value, iModel Id and project Id.

OAuth access token with scope `changedelements:modify`

Authorization

Setting to `application/vnd.bentley.itwin-platform.v1+json` is recommended.

Accept

Change tracking for iModel was updated successfully.

This response indicates that request lacks valid authentication credentials. Access token might not been provided, issued by the wrong issuer, does not have required scopes or request headers were malformed.

The user has insufficient permissions for the requested operation.

This response indicates that disabling change tracking is not possible because the iModel is not valid.

A URL parameter was malformed or the body of the request is invalid.

application/json;InvalidChangedElementsRequest

This response indicates that the user has sent too many requests in a given amount of time.

The number of requests exceeds the rate-limit for the client subscription.

retry-after

---

Obtains which elements have changed in the iModel between the given start and end changesets.

This information will only be available after change tracking has been enabled and the processing operation completes.

### Authentication

Requires `Authorization` header with valid Bearer token for scope `changedelements:read`.

For more documentation on authorization and how to get access token visit [OAUTH2 Authorization](https://developer.bentley.com/apis/overview/authorization/) page.

---

get-comparison

iModelId

projectId

startChangesetId

endChangesetId

OAuth access token with scope `changedelements:read`

This response indicates that provided comparison results are not ready or unexistent.

A URL parameter was malformed or there are missing required parameters.

Changed Elements

API references