# Preview a transform


**POST /_transform/{transform_id}/_preview**

**All methods and paths for this operation:**

<div>
                      <span class="operation-verb get">GET</span>
                      <span class="operation-path">/_transform/_preview</span>
                      </div>
                    <div>
                      <span class="operation-verb post">POST</span>
                      <span class="operation-path">/_transform/_preview</span>
                      </div>
                    <div>
                      <span class="operation-verb get">GET</span>
                      <span class="operation-path">/_transform/{transform_id}/_preview</span>
                      </div>
                    <div>
                      <span class="operation-verb post">POST</span>
                      <span class="operation-path">/_transform/{transform_id}/_preview</span>
                      </div>
                    

Generates a preview of the results that you will get when you create a transform with the same configuration.

It returns a maximum of 100 results. The calculations are based on all the current data in the source index. It also
generates a list of mappings and settings for the destination index. These values are determined based on the field
types of the source index and the transform aggregations.

## Required authorization

* Index privileges: `read`,`view_index_metadata`
* Cluster privileges: `manage_transform`



## Servers
- http://api.example.com: http://api.example.com ()


## Authentication methods
- Api key auth
- Basic auth
- Bearer auth


## Parameters

### Path parameters
- **transform_id** (string)
  Identifier for the transform to preview. If you specify this path parameter, you cannot provide transform
  configuration details in the request body.

### Query parameters
- **timeout** (string)
  Period to wait for a response. If no response is received before the
  timeout expires, the request fails and returns an error.

### Body: application/json (object)

- **dest** (object)
  The destination for the transform.
- **description** (string)
  Free text description of the transform.
- **frequency** (string)
  The interval between checks for changes in the source indices when the
  transform is running continuously. Also determines the retry interval in
  the event of transient failures while the transform is searching or
  indexing. The minimum value is 1s and the maximum is 1h.
- **pivot** (object)
  The pivot method transforms the data by aggregating and grouping it.
  These objects define the group by fields and the aggregation to reduce
  the data.
- **source** (object)
  The source of the data for the transform.
- **settings** (object)
  Defines optional transform settings.
- **sync** (object)
  Defines the properties transforms require to run continuously.
- **retention_policy** (object)
  Defines a retention policy for the transform. Data that meets the defined
  criteria is deleted from the destination index.
- **latest** (object)
  The latest method transforms the data by finding the latest document for
  each unique key.


## Responses
### 200


#### Body: application/json (object)
- **generated_dest_index** (object)

- **preview** (array[object])



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