# Consent Management: Configuring OneTrust Consent Migration

This tutorial requires Fides Cloud or Fides Enterprise. For more information, [talk to our solutions team.](/content/speak-with-us?utm_source=docs-site/index.html)

## Prerequisites

For this tutorial you'll need:

- A Fides Cloud or Fides Enterprise account
- The role of `Owner` or `Contributor` for your Fides organization.
- Existing OneTrust consent categories that some users have consented to.

## Overview

Fides supports the migration of consent preferences from OneTrust to Fides. This feature allows organizations transitioning from OneTrust to Fides to seamlessly migrate user consent preferences without requiring users to re-consent. This document provides guidance on how to configure and use this feature.

## How It Works

The OneTrust migration feature works by mapping OneTrust consent categories to Fides privacy notices. When a user has an existing OneTrust consent cookie, Fides will read this cookie and apply the corresponding consent preferences to the Fides cookie.

### Key Components

- **OneTrust Consent Cookie**: The `OptanonConsent` cookie stores user consent preferences in OneTrust.
- **Fides Consent Cookie**: The `fides_consent` cookie stores user consent preferences in Fides.
- **Mapping Configuration**: A JSON object that maps OneTrust categories to Fides notice keys.

## Configuration Steps

1. **Define the Mapping**: Create a mapping between OneTrust categories and Fides notice keys. This mapping should be a JSON object, for example:

```
    {
      "C0001": ["essential"],
      "C0002": ["analytics_opt_out"],
      "C0004": ["advertising", "marketing"]
    }
    ```

Encode this mapping using `encodeURIComponent(JSON.stringify(mapping))`.

2. **Configure the Mapping**: You can provide the `ot_fides_mapping` in one of the following ways:

- **`window.fides_overrides` Object**: Add the mapping to the `window.fides_overrides` object before initializing Fides.

```
    window.fides_overrides = {
      ot_fides_mapping: encodeURIComponent(JSON.stringify({
        "C0001": ["essential"],
        "C0002": ["analytics_opt_out"],
        "C0004": ["advertising", "marketing"]
      }))
    };
    ```

Note that the overrides location of `window.fides_overrides` is configurable. If you wish to use a different location for your overrides, you may set up the ENV variable `FIDES_PRIVACY_CENTER__CUSTOM_OPTIONS_PATH` to the desired location, e.g. `window.config.fides_overrides`. Be careful not to use `window.Fides.*` as this would override core Fides functionality.
   - **Cookie**: Store the mapping in a cookie named `ot_fides_mapping`, which Fides can read during initialization.
   - **Query Parameter**: Pass the `ot_fides_mapping` as a query parameter when initializing Fides.js, e.g. `https://privacy.example.com/fides.js?ot_fides_mapping=...`.

For more info on your options, see the [FidesOptions Interface Guide](/content/docs/privacy-center-fidesjs/fidesjs/reference/interfaces/FidesOptions/index.html).

Once this is set up, Fides will automatically read the OneTrust cookie and apply the consent preferences to the Fides cookie.

## Edge Cases

- **Invalid OneTrust Cookie**: If the OneTrust cookie is invalid or malformed, Fides will skip the migration and use default consent settings.
- **Non-Existent Mapping**: If a category in the OneTrust cookie does not exist in the mapping, it will not affect the Fides consent preferences.