# Duplicate Document Prevention

By default, Documint will first check if a document has already been created using the same template and data before creating a new one. If a document has already been created, Documint will return the existing document. If not, it will create a new document. This prevents the same document from being generated more than once and counting against your quota multiple times. 

There may be cases where you want/need more fine-tuned control over this functionality. In those cases, you can tell Documint specifically which fields in your data to watch for changes. This is accomplished using the `watch_fields` or `ignore_fields` query parameters in the Generation Link URL. 

### Setup

To use this feature, you will need to add either `watch_fields` or `ignore_fields` as a query parameter to your Generation Link. If both parameters are passed, only the `watch_fields` parameter will be evaluated. Add a comma-separated list of field names, in [snake-case](https://docs.documint.me/integrations/airtable/broken-reference), as the value for the parameter.

{% hint style="warning" %}
Field names must be converted to [**snake-case**](https://docs.documint.me/integrations/airtable/broken-reference) when used in this query parameter.
{% endhint %}

{% hint style="info" %}
Every time a document is created, Documint creates a hash of the data that is being merged and the template. This allows Documint to detect changes in either without ever storing your data.  
{% endhint %}

![](https://1903534506-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FTY5wPd81K7B5rjyG5tjS%2Fuploads%2FplAgNBTMHNMvqmUJYHQK%2Fduplicate%20parameter.png?alt=media\&token=237c041c-7d7a-466c-b508-128193524c92)