> For the complete documentation index, see [llms.txt](https://docs.b2b-sellers.com/b2b-platform/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.b2b-sellers.com/b2b-platform/developer-guide/b2bsellers-core-plugin/custom-url-parameter.md).

# Custom URL Parameter

## **useCustomer**

The `useCustomer` parameter ensures that a user is redirected to the correct context when they have access to multiple customer accounts. It allows you to define exactly which customer context should be active when a link is clicked.

#### Why use it?

In B2B environments, a single user often manages or buys for multiple companies. If a user is currently logged in under "Company A" but clicks an email link intended for "Company B", they might encounter an error or see the wrong data.

By appending `useCustomer`, the platform automatically switches the user to the correct customer context before loading the page, provided the user has the necessary permissions for that customer.

#### Implementation Details

* Availability: This parameter is currently supported exclusively for the `/b2b_platform` controller (all Vue.js-based B2B Platform URLs).
* Accepted Values: You can pass either the Customer Number or the Customer ID (UUID).

#### Practical Example: Offer Management

This function is primarily used within the Offer Management workflow. When a sales representative sends an offer to a customer:

1. The "Order Offer" button in the email includes the `useCustomer` parameter.
2. Upon clicking, the user is instantly switched to the correct customer account.
3. The offer checkout pop-up opens immediately with the correct context, preventing manual switching.

{% hint style="info" %}
Always include the `useCustomer` parameter when generating URLs for emails or third-party integrations to ensure a seamless user experience.
{% endhint %}

{% hint style="warning" %}
For better security and to avoid exposing internal database structures, we recommend using the Customer Number rather than the Customer UUID in public-facing links.
{% endhint %}


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