---
language: en
title: External ID in form fields
category: Flows
summary: Learn how to assign a unique external ID to each custom field in your TuCalendi form flows to connect them with third party platforms.
---

# External ID in form fields

**The external ID in custom form fields is a unique identifier for each field**. It's essential when you want to send TuCalendi form information to **third party platforms**, such as the [direct integration with Klicktipp](https://www.tucalendi.com/en/s/integrations/integration-with-klicktipp), or when you send information using **webhooks** through [Pabbly](https://www.tucalendi.com/es/s/tutoriales/que-es-pabbly-connect) or **Zapier**.

Identifying each custom form field is very simple.

[Log in to TuCalendi](https://account.tucalendi.com/) with your username and password. In the side menu, go to the **"Flows"** option:

![Flows menu](https://www.tucalendi.com/images/content/flows/en/flow-menu-four-types.png)

In the forms option, click **"Select"** to open your **form flows**.

![Form flow with event assigned](https://www.tucalendi.com/images/content/flows/en/form-flow-event-assigned.png)

> [!WARNING]
> If you haven't created a form flow yet, the list will be empty and you can create a new one.

If you've already created a form flow, click **"Edit"**:

![Form with different fields](https://www.tucalendi.com/images/content/flows/en/custom-fields-added.png)

In our form flow we have two **custom fields**:

- Company name.
- Job title.

To edit the custom fields, click the **pencil icon** next to each field:

![Edit custom field](https://www.tucalendi.com/images/content/flows/en/edit-custom-field.png)

In the window that opens with all the custom field information, click **"Optional"** to enter the **external ID**:

![External ID in custom field](https://www.tucalendi.com/images/content/flows/en/external-id-custom-field.png)

Type in the external ID you want to assign and click **"Apply"**.

You'll return to the main screen of the form flow you're editing. Then click **"Save"**.

> [!TIP]
> The external ID must be set **individually for each custom field**.

From now on, when you want to connect to third party platforms, your fields will already be identified with an external ID, so you can work with them more easily.