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Custom fields are custom key-value pairs attached to contacts. Use them to organize contacts, track metadata, and build targeted audiences.

What Are Custom Fields?

Custom fields are flexible metadata you define. Each custom field has:
  • Key: The custom field name (e.g., source, tier, cohort)
  • Value: The custom field value (e.g., facebook, gold, january2024)
Custom fields are per-list — they are stored on the ListContact (the relationship between a contact and a sending list), not on the Contact itself. This means the same phone number can have different custom field values on different lists.

Common Custom Field Patterns

Acquisition Source

Track where contacts came from:

Contact Segmentation

Categorize contacts by behavior or value:

Temporal Data

Track time-based information:

Custom Attributes

Store any relevant metadata:

Adding Custom Fields

During Import

Include custom fields in the custom_fields object when creating contacts via the API:

Via API

Include custom fields when creating contacts:

In Dashboard

  1. Go to Sending Lists > select list > Contacts
  2. Click on a contact
  3. Click Edit Custom Fields
  4. Add or modify custom fields
  5. Click Save

Using Custom Fields in Audiences

Custom fields are the primary way to segment contacts into audiences. Use them in audience conditions:

Basic Condition

Matches contacts with source custom field equal to facebook.

Multiple Values

Matches contacts with tier custom field of either gold or silver.

Existence Check

Matches contacts that have any value for the vip custom field.

Negation

Matches contacts that don’t have the churned custom field.

Numeric Comparison

Numeric custom fields support gt, gte, lt, lte operators in addition to eq and ne.

All Available Operators

Custom Field Best Practices

Establish naming conventions and stick to them:
  • Use lowercase: source not Source
  • Use underscores: sign_up_date not sign-up-date
  • Be specific: acquisition_source not src
Use consistent values across imports:
  • facebook not sometimes Facebook or FB
  • 2024-01-15 not Jan 15, 2024 or 1/15/24
Add custom fields you’ll actually use for targeting. Too many custom fields create noise.
Maintain a reference of what custom fields you use and what values are valid. Share with your team.
Custom fields like churned, complained, high_risk help you exclude contacts from sends.

Bulk Custom Field Updates

Coming Soon — Bulk custom field updates via audiences are not yet available. Currently, custom fields can be set via the API when creating or updating contacts.

Viewing Custom Field Usage

To see all custom fields in use across your contacts:
  1. Go to Audiences > New Audience
  2. Click Add Condition > Custom Field
  3. The dropdown shows all existing custom field keys
  4. Select a key to see its values
This helps you understand what custom fields exist in your data.

Example: Full Segmentation Strategy

Here’s an example custom field strategy for an e-commerce brand:
This enables audiences like:
  • VIP Winback: ltv_tier=vip AND last_purchase_days=90
  • New High Engagers: cohort=2024-Q1 AND engagement_level=high AND buyer_status=never
  • Promo Candidates: promo_responsive=true AND buyer_status=once

Next Steps

Building Audiences

Use custom fields for targeting

Segmentation Logic

Combine custom field conditions

Import Contacts

Add custom fields during import