---
title: Contacts and Data
description: Store and manage your audience
icon: Users
---

## What are contacts

Contacts are people in your email list. Each contact has:

- **Email** — Unique identifier
- **Subscription status** — Subscribed or unsubscribed
- **Custom data** — Any fields you need

## Data structure

```json
{
  "id": "contact_abc123",
  "email": "user@example.com",
  "subscribed": true,
  "data": {
    "firstName": "Sarah",
    "plan": "pro",
    "mrr": 99
  }
}
```

The `data` field stores custom information as key-value pairs.

## Data types

**Strings:**
```json
{ "firstName": "Sarah", "company": "Acme Inc" }
```

**Numbers:**
```json
{ "mrr": 99, "loginCount": 15 }
```

Store as numbers for `greaterThan`/`lessThan` comparisons.

**Booleans:**
```json
{ "verified": true, "newsletter": false }
```

**Dates:**
```json
{ "signupDate": "2024-03-15T10:30:00Z" }
```

Use ISO 8601 format.

**Arrays:**
```json
{ "tags": ["vip", "enterprise"] }
```

**Objects:**
```json
{
  "address": {
    "city": "San Francisco",
    "country": "US"
  }
}
```

Access nested fields: `address.country`

## Creating contacts

### Via API

```bash
curl -X POST {{API_URL}}/contacts \
  -H "Authorization: Bearer sk_your_secret_key" \
  -H "Content-Type: application/json" \
  -d '{
    "email": "user@example.com",
    "subscribed": true,
    "data": {
      "firstName": "Sarah",
      "plan": "pro"
    }
  }'
```

### Automatic upsert

If email exists, updates instead of creating duplicate.

```javascript
// First call
POST /contacts { email: "user@example.com", data: { plan: "free" } }

// Second call - updates same contact
POST /contacts { email: "user@example.com", data: { mrr: 99 } }

// Result: { plan: "free", mrr: 99 }
```

Data merges automatically.

### Via event tracking

```bash
curl -X POST {{API_URL}}/v1/track \
  -H "Authorization: Bearer pk_your_public_key" \
  -H "Content-Type: application/json" \
  -d '{
    "email": "user@example.com",
    "event": "signed_up",
    "data": {
      "plan": "pro",
      "source": "landing"
    }
  }'
```

Creates contact if doesn't exist, updates if does.

## Updating contacts

```bash
curl -X PATCH {{API_URL}}/contacts/contact_id \
  -H "Authorization: Bearer sk_your_secret_key" \
  -H "Content-Type: application/json" \
  -d '{
    "data": {
      "plan": "premium",
      "mrr": 199
    }
  }'
```

New fields added, existing fields overwritten, unmentioned fields preserved.

### Remove fields

Set to `null`:

```json
{ "data": { "temporaryToken": null } }
```

## Subscription status

**Subscribed (true):**
- Receives marketing emails
- Receives transactional emails

**Unsubscribed (false):**
- Does NOT receive marketing emails
- Still receives transactional emails

Template type controls this behavior. See [Template Types](/concepts/templates-types).

## Using contact data

### In templates

```html
<h1>Hi {{firstName}}!</h1>
<p>Your {{plan}} plan renews on {{renewalDate}}.</p>
```

### In segments

Filter by data fields:
- `plan equals "premium"`
- `mrr greaterThan 100`
- `loginCount lessThan 5`

### In workflows

```
[Condition: plan equals "enterprise"]
    ├─ True → [Send: Enterprise content]
    └─ False → [Send: Standard content]
```

## Best practices

**Consistent naming** — Use camelCase or snake_case, not both.

**Correct types** — Use `99` not `"99"` for numbers.

**ISO dates** — `"2024-03-15T10:30:00Z"` for date fields.

**Sync critical fields only** — Don't mirror entire database. Only fields used in emails, segments, or workflows.

**Update in real-time** — When user data changes, update contact immediately.

**Respect unsubscribes** — Never re-subscribe automatically.

## Deleting contacts

```bash
curl -X DELETE {{API_URL}}/contacts/contact_id \
  -H "Authorization: Bearer sk_your_secret_key"
```

Permanent deletion. Consider unsubscribing instead to preserve history.

## Next steps

- [Create segments](/concepts/segments-and-filters)
- [Track events](/concepts/events-and-triggers)
- [Use templates](/concepts/templates-types)