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# Audiences

> How audiences, contacts, tags, merge fields, and segments relate to each other in Mailchimp.

## The basics

An audience is a list of contacts. Almost everything you do with the Marketing
API happens inside one: contacts belong to an audience, and so do the merge
fields that describe them and the segments that group them.

Most integrations work against an audience that already exists. You'll need its
`list_id`, which you can find with `GET /3.0/lists`.

## How the pieces fit together

```
Audience
├── Contacts            people, identified by email address
│   ├── Tags            labels you apply to individual contacts
│   └── Merge field values
├── Merge fields        the field definitions for this audience
└── Segments            saved queries that select contacts

Each contact also carries consent, recorded separately per channel
(email, SMS).
```

**Contacts** are the people in an audience. Each one is identified by their
email address, and in the API by the MD5 hash of that address in lowercase —
the `subscriber_hash` you'll see throughout the endpoints.

**Tags** are labels you attach to individual contacts. They're yours to define:
map them from your CRM, or use them to record behavior that matters to you.
Tags live on the contact, not on the audience.

**Merge fields** are the custom data fields an audience can store about its
contacts — first name, birthday, favorite product. The *definitions* belong to
the audience; the *values* belong to each contact. That split is the part
people trip over: adding a merge field to an audience doesn't populate it, and
setting a value on a contact requires the field to exist first.

**Segments** are saved queries that select a subset of contacts, using
conditions like signup date, campaign engagement, or which tags a contact
carries. A segment doesn't contain contacts or tags; it selects contacts, and
the set changes as your data does.

> **Note**
>
> **Tags versus segments**: a tag is something you *put on* a contact. A segment
> is a question you *ask about* contacts. Tags are one of the things a segment
> can filter on, which is why they're easy to confuse.

## Consent

Consent is the record of what a contact agreed to receive from you, and it
belongs to the contact rather than to the audience. Mailchimp tracks it per
channel: agreeing to marketing email says nothing about agreeing to marketing
SMS, and the two are stored and updated independently.

Consent is an input, not the final answer to "can I send to this person?" What
Mailchimp sends on is a subscription status, which it derives from the consent
you supply, the audience's opt-in configuration, and whether the contact is
reachable on that channel at all. A contact who consented to email can still
stop receiving it because their address started bouncing. You record consent;
Mailchimp decides deliverability.

That split is the part integrations get wrong. Writing a contact through the
API is a consent event, so the value you send has to reflect something the
person actually did. If your checkout form has a marketing checkbox, the state
of that checkbox is your consent record. Sending every customer through as
opted in because they bought something is the failure mode to avoid.

### Why this matters

Email and SMS marketing are regulated—GDPR, CAN-SPAM, CASL, and TCPA among
others—and the obligations attach to you as the sender, not to Mailchimp as the
platform. Consent is the evidence that you met them, which is why the API asks
you to state it explicitly rather than inferring it.

SMS carries the stricter rules of the two. Consent to email does not extend to
SMS under any regime we know of, and several require separate, provable opt-in
for messages sent to a phone. Treat the two channels as genuinely separate
records, because that is what they are.

Which endpoint you use to record consent depends on the channel, and the
mechanics differ between them. See
[Contacts](/marketing/concepts/audiences/contacts) for the contact-level model
and [Audiences endpoints (beta)](/marketing/api-concepts/audiences-endpoints-beta)
for the SMS channel.

## Where to go next

* [Contacts](/marketing/concepts/audiences/contacts) — the contact model, subscription status, and tags
* [Merge fields](/marketing/concepts/audiences/merge-fields) — defining and populating custom fields
* [Segments](/marketing/concepts/audiences/segments) — building queries over your contacts
* [Audiences endpoints (beta)](/marketing/api-concepts/audiences-endpoints-beta) — the per-channel consent model, including SMS
* [Import and export contacts](/marketing/build/quickstarts/import-and-export-contacts) — a walkthrough against an existing audience