--- layout: default title: Lowercase string processor parent: Processors grand_parent: Pipelines nav_order: 60 --- # lowercase_string The `lowercase_string` processor converts a string to its lowercase counterpart and is a [mutate string](https://github.com/opensearch-project/data-prepper/tree/main/data-prepper-plugins/mutate-string-processors#mutate-string-processors) processor. The following table describes options for configuring the `lowercase_string` processor to convert strings to a lowercase format. Option | Required | Type | Description :--- | :--- | :--- | :--- with_keys | Yes | List | A list of keys to convert to lowercase. <!---## Configuration Content will be added to this section. ## Metrics Content will be added to this section.--->