Use custom fields in emails, SMS, and automations

Custom fields aren't just storage — they're how you personalize messages and drive automation logic without writing a different email for every contact. This article covers inserting a field as a merge tag, using a field's value as a workflow condition, and updating a field automatically as part of an automation.

#Merge tags: inserting a field into a message

A merge tag is a placeholder in an email, SMS, or template that gets replaced with a specific contact's data when the message actually sends. Merge tags look like {{contact.first_name}} for standard fields and follow a similar pattern for custom fields, referencing the field by its underlying key rather than its display label.

To insert one:

1. While editing an email, SMS template, or workflow message step, open the merge tag (sometimes called "variable" or "personalization") picker — usually a button near the text editor.
2. Find the custom field you want, organized by folder if you've set folders up, and select it. The tag is inserted at your cursor.
3. Preview or send a test message to confirm it renders the way you expect.

A message can combine as many merge tags as you like: "Hi {{contact.first_name}}, your {{contact.preferred_appointment_type}} is confirmed for {{contact.appointment_date}}."

Warning: If a contact's custom field is empty, the merge tag typically renders as blank text rather than throwing an error — the sentence above would read "Hi , your is confirmed for ." with awkward gaps. Before sending a campaign built around a custom field, check how many contacts in your recipient list actually have that field filled in, or add a fallback sentence structure that still reads correctly if it's missing.

#Custom fields vs. custom values in messages

It's easy to confuse two similarly named things:

• A custom field holds a different value per contact (or per opportunity) — first name, budget, appointment date. This is what you use for personalization.
• A custom value is a single reusable piece of static text shared across the whole account — your business phone number, a standard legal disclaimer, a sign-off. The same custom value renders identically no matter which contact receives the message.

Use a custom field when the answer varies by contact. Use a custom value when the answer is the same for everyone and you just want to avoid retyping it (and want a single place to update it later). Both are inserted through similar-looking tag pickers, so double-check you've grabbed the right one — a custom value tag in place of a custom field tag will show the same static text to every recipient instead of personalizing anything.

#Branching a workflow on a custom field's value

Workflows can read a contact's custom field and make decisions based on it, which is what turns a field from passive storage into active automation:

1. In the workflow builder, add an If/Else (condition) step, or use a filter on the trigger itself.
2. Choose the custom field as the condition's source, then set the comparison — equals, does not equal, is greater than, contains, is empty, and so on, depending on the field type.
3. Build separate branches for each outcome — for example, route contacts with "Lead Source" equal to "Referral" into a different nurture sequence than everyone else.

This is also how you personalize logic beyond just message text: a workflow can wait for a specific date field to arrive, skip a step entirely if a checkbox field isn't set, or fork a sequence three ways based on a dropdown answer.

#Updating a custom field from a workflow

Workflows aren't limited to reading fields — an Update Contact Field (or equivalent) action lets an automation write a value back to the record, no human involved. Common uses:

• Set a "Last Contacted Date" field automatically whenever an email in a sequence goes out.
• Flip a "Nurture Stage" dropdown forward each time a contact completes a step.
• Populate a field based on a calculation or a condition elsewhere in the workflow — for example, setting "Lead Score Tier" to "Hot" once a numeric score field crosses a threshold.

To set this up, add an action step, choose the field-update action, pick the target field, and either enter a fixed value or map it from data already available in the workflow (like another field, or the trigger's payload). Because the update happens through the same field every other part of the account reads, the change is visible immediately in smart lists, on the contact record, and to any other workflow watching that field.

Tip: Field updates driven by workflows are a common source of "who changed this?" confusion months later. Name your automations clearly and, if your account supports it, leave a note on complex workflows explaining which fields they touch — future you (or a teammate) will thank you.

#What "done" looks like

A personalized email or SMS using custom fields should render cleanly for a contact with every relevant field filled in, and shouldn't look broken for one who's missing a field. A workflow that branches or updates based on custom fields should have been tested with at least one contact per branch so you've actually seen each path fire, not just assumed the logic is correct.

#Related articles

• Custom fields overview
• Create and manage custom fields
• Use custom fields in forms, surveys, and the contact record

#Frequently asked questions

#Can I use a custom field in the subject line of an email campaign, not just the body?

Yes — most merge tag pickers are available in the subject line field as well as the body. A personalized subject line (using a first name or a relevant custom field) is a common way to improve open rates, covered further in Read campaign results.

#What happens if I reference a custom field in a workflow, then delete the field?

The workflow step referencing it will typically stop functioning correctly — the condition may always evaluate as empty, or the update action may fail silently. Always check active workflows for field references before deleting a custom field, as covered in Create and manage custom fields.

#Can a workflow update an opportunity custom field from a contact-triggered workflow?

This depends on the workflow having access to the relevant opportunity in context — typically by triggering off an opportunity event, or by including an action that looks up the associated opportunity first. A workflow triggered purely by a contact event may not have a specific opportunity in scope to update.