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The ActiveCampaign integration is a powerhouse for enterprise marketing automation. It goes far beyond simply adding an email address to a list. It allows you to dynamically append behavioral tags, populate custom fields, and trigger complex automated workflows the absolute second a form is submitted, effectively removing any manual data entry from your marketing team.

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Enterprise Business Use Cases

Dynamic Tag-Based Segmentation

Automatically tag users based on their exact form selections. For example, if a user selects “Enterprise” in a pricing dropdown, Flex Forms will instantly append the interest: enterprise_plan tag to their profile, instantly triggering a VIP sales automation sequence.

Instant Drip Campaigns

Push high-value leads straight into a specific ActiveCampaign List. This acts as the entry trigger for a 5-day educational welcome email sequence, ensuring your brand stays top-of-mind immediately after the conversion.

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Ultra-Detailed, Step-by-Step Setup Guide

ActiveCampaign makes API integration incredibly simple and secure. You only need a specific Base URL and a single API key. Follow these exact instructions to find them.
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Step 1: Log into ActiveCampaign

Open your web browser and navigate to your ActiveCampaign login URL. Enter your email and password to log in.Note: You must have Administrator privileges to access developer settings.
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Step 2: Locate the Settings Gear

Once you are logged into the main dashboard, look at the absolute bottom left corner of your screen. You will see a gear icon (Settings). Click it to open the administrative menu.
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Step 3: Navigate to Developer Settings

In the left-hand sidebar menu of the Settings page, scroll down until you see the section labeled Developer. Click exactly on this link.
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Step 4: Locate the API Access Box

You are now on the Developer settings page. At the very top, you will see a prominent box labeled API Access. Inside this box are the two pieces of information you need: the URL and the Key.
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Step 5: Copy the URL

Highlight the entire string in the URL field (it will look something like https://yourcompany.api-us1.com). Right-click and select Copy (or press Ctrl+C / Cmd+C).Do not copy any trailing slashes.
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Step 6: Create a Connection (recommended)

Switch to Flex Forms → Integrations → Connections. Create an ActiveCampaign connection, paste the API URL, then continue with the key in the next steps.
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Step 7: Copy the API Key

Switch back to the ActiveCampaign tab. In that same “API Access” box, highlight the extremely long string of characters in the Key field. Right-click and select Copy.
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Step 8: Save credentials and wire feeds

Paste the key into the same Connection (or Catalog → ActiveCampaign for a single shared account). On each form hub Integrations tab, enable ActiveCampaign and pick the Connection.

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Masterclass: Mapping Data Payloads

ActiveCampaign handles standard fields easily, but true marketing power comes from mapping data to highly specific Custom Fields and Lists. By default, Flex Forms automatically syncs the primary Email Block to the Contact’s email address.
Map additional fields one per line in your specific form’s Integration settings.The format is always: activecampaign_field=flex_forms_fieldStandard fields include:
  • firstName
  • lastName
  • phone

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How Custom Fields Work in ActiveCampaign

When you map to a custom field in ActiveCampaign, you cannot just use the field’s text name. ActiveCampaign strictly requires you to map to its internal Numeric ID (e.g., 12).
Finding Custom Field IDs
1. In ActiveCampaign, go to Settings > Manage Fields
2. Use your browser's Developer Tools (Network tab)
3. Or simply use Flex Forms' built-in Field Catalog dropdown!
The + Prefix Trick: If you don’t want to hunt down numeric IDs, Flex Forms offers a massive quality-of-life feature. If you prefix a text key with a plus sign (+), Flex Forms will tell ActiveCampaign to automatically create that custom text field if it doesn’t exist.Example: +CompanySize=size_dropdown

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Enterprise Features & Troubleshooting

In the form’s specific integration settings in the Flex Forms Studio, you can define a comma-separated list of List IDs. Any user who submits the form will be instantly subscribed to those lists.Note: If your ActiveCampaign list is configured to require Double Opt-in, the user will be added in an ‘Unconfirmed’ state until they click the link in the email ActiveCampaign sends them.
You can define static tags to apply to every submission (e.g., source: website_form). However, for true enterprise automation, you should configure your Flex Forms Dropdown values to perfectly match your ActiveCampaign tags (e.g., set the Dropdown Value to interest_b2b). This allows for dynamic, conditional segmentation without building complex logic rules inside ActiveCampaign.
ActiveCampaign uses the email address as the universal primary key. If a user submits a Flex Form and they already exist in your ActiveCampaign database, Flex Forms will safely update their custom fields and append the new tags/lists to their profile without duplicating the contact record.

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Configuration Reference

The following advanced settings are available in the Flex Forms UI for this integration. Use this reference to understand exactly how each field impacts the API payload.

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Global Settings

Located in Integrations in the Flex Forms left rail.
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text
required
API URL Your account-specific ActiveCampaign API endpoint. You can find this by logging into ActiveCampaign, navigating to Settings → Developer, and copying the URL from the API access section.
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password
required
API key The master API key that grants Flex Forms permission to manage your contacts and lists. Also found in Settings → Developer. Treat this like a password.

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Form-Level Settings

Located on the form hub Integrations tab for a specific form.

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Subscriber Placement

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remote_select
required
ActiveCampaign list The primary mailing list that the new contact will be subscribed to. Flex Forms automatically queries the ActiveCampaign API to load a live dropdown of all your available lists.
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text
Tags A comma-separated list of tags to instantly apply to the new contact (e.g., lead, webinar-2024, highly-engaged). You can use merge tags to dynamically apply tags based on form answers (e.g., {{industry_dropdown}}).

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Field Mapping

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select
required
Email field The primary email block to sync. Required for ActiveCampaign’s deduplication and creation logic.
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select
First name field
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select
Last name field
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select
Phone field
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select
Organization field
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textarea
Custom fields The routing engine for mapping Flex Form answers into ActiveCampaign Custom Contact Fields.Unlike HubSpot, ActiveCampaign identifies custom fields using numeric IDs, not text names. You must provide one rule per line using the format: activecampaign_field_id=flex_forms_block_name.Pro-tip: If you prefix a key with + (e.g., +FavoriteColor=color_input), Flex Forms will automatically create that custom text field inside ActiveCampaign for you on the fly if it doesn’t already exist.
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remote_select
Available fields (reference) A helper tool. Open this dropdown to view a live list of all your existing ActiveCampaign custom fields and their required numeric IDs, so you can easily construct your custom_field_map.

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Contact Processing & Overrides

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select
default:"1"
Overwrite with empty values Controls how Flex Forms handles blank form submissions when updating an existing contact.Options:
  • 1: Yes — If a user leaves a form field blank, Flex Forms will wipe out the corresponding data in ActiveCampaign (destructive).
  • 0: No — If a user leaves a form field blank, Flex Forms will preserve the existing data in ActiveCampaign for that field (safe).
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textarea
Note An optional block of text appended to the Contact’s Activity Stream as a Note. Perfect for summarizing their inquiry. Supports merge tags (e.g., Reason for contacting: {{reason}}).

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Email Automation Triggers

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remote_select
Double opt-in form If you are strictly enforcing GDPR/CAN-SPAM, select an existing ActiveCampaign form here. Flex Forms will trigger ActiveCampaign to send the official double opt-in confirmation email associated with that specific ActiveCampaign form.
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select
default:"0"
Instant responders If enabled (1), ActiveCampaign will immediately send any auto-responder emails attached to the selected list_id the moment the contact is created.
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select
default:"0"
Send last broadcast If enabled (1), ActiveCampaign will automatically forward the very last broadcast campaign you sent to this list to the new contact as a welcome gesture.
Last modified on September 7, 2026