> ## Documentation Index
> Fetch the complete documentation index at: https://docs.usesend.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Double Opt-In

> Verify new subscribers with a confirmation email before adding them to your contact book

## Overview

Double opt-in requires new contacts to confirm their email address before they become subscribed. When enabled on a contact book, newly added contacts receive a confirmation email with a verification link. Only after clicking the link do they become fully subscribed.

**Why use double opt-in?**

* Ensures email addresses are valid and owned by the subscriber
* Reduces bounce rates and spam complaints
* Improves deliverability and sender reputation
* Helps comply with email marketing regulations (GDPR, CAN-SPAM)

## How it works

<Steps>
  <Step title="Contact is added">
    When a contact is added to a contact book with double opt-in enabled (via
    dashboard, API, or CSV import), they are created with a **Pending** status
    instead of being immediately subscribed.
  </Step>

  <Step title="Confirmation email is sent">
    A confirmation email is automatically sent to the contact with a unique
    verification link. The link is signed with HMAC-SHA256 and expires after 7
    days.
  </Step>

  <Step title="Contact confirms">
    The contact clicks the verification link in the email and confirms their
    subscription on the confirmation page.
  </Step>

  <Step title="Contact is subscribed">
    The contact's status changes from **Pending** to **Subscribed** and they
    will now receive your emails.
  </Step>
</Steps>

## Enabling double opt-in

### Via the dashboard

1. Go to [Contacts](https://app.usesend.com/contacts) and select a contact book
2. Click on the **Double Opt-In** tab
3. Toggle double opt-in on
4. Customize the confirmation email (optional)
5. Save your changes

### Via the API

Create a contact book with double opt-in enabled:

```bash theme={null}
curl -X POST https://app.usesend.com/api/v1/contactBooks \
  -H "Authorization: Bearer us_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Newsletter Subscribers",
    "doubleOptInEnabled": true,
    "doubleOptInFrom": "Newsletter <hello@yourdomain.com>",
    "doubleOptInSubject": "Please confirm your subscription"
  }'
```

Or enable it on an existing contact book:

```bash theme={null}
curl -X PATCH https://app.usesend.com/api/v1/contactBooks/{contactBookId} \
  -H "Authorization: Bearer us_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "doubleOptInEnabled": true
  }'
```

## Contact statuses

When double opt-in is enabled, contacts have three possible statuses:

| Status           | Description                                                      |
| ---------------- | ---------------------------------------------------------------- |
| **Subscribed**   | Contact has confirmed their subscription and will receive emails |
| **Pending**      | Contact has been added but hasn't confirmed yet                  |
| **Unsubscribed** | Contact has explicitly unsubscribed                              |

<Warning>
  Contacts with **Pending** status will not receive campaign emails. They will
  only receive the double opt-in confirmation email.
</Warning>

## Customizing the confirmation email

You can customize three aspects of the confirmation email:

### From address

Set a custom sender address for confirmation emails. The address must use one of your verified domains.

```json theme={null}
{
  "doubleOptInFrom": "Newsletter <hello@yourdomain.com>"
}
```

If not set, the confirmation email will be sent from the first available verified domain.

### Subject line

Customize the email subject. The default is "Please confirm your subscription".

```json theme={null}
{
  "doubleOptInSubject": "Confirm your subscription to our newsletter"
}
```

### Email template

The confirmation email body can be customized using the useSend email editor (via the dashboard) or by providing the editor JSON content via the API.

#### Template variables

The following variables can be used in the confirmation email template:

| Variable             | Description                      |
| -------------------- | -------------------------------- |
| `{{doubleOptInUrl}}` | The confirmation link (required) |
| `{{email}}`          | The contact's email address      |
| `{{firstName}}`      | The contact's first name         |
| `{{lastName}}`       | The contact's last name          |

<Warning>
  The `{{ doubleOptInUrl }}` variable is **required** in the email template. The
  confirmation email cannot be saved without it. This ensures every confirmation
  email contains a working verification link.
</Warning>

## Resending confirmation emails

If a contact hasn't confirmed their subscription, you can resend the confirmation email from the dashboard:

1. Go to your contact book and find the pending contact
2. Click the **Resend** button next to the contact

Each resend generates a new confirmation link with a fresh 7-day expiration window.

## Best practices

| Best practice                      | Why it helps                                                                     |
| ---------------------------------- | -------------------------------------------------------------------------------- |
| Set up a verified domain first     | Double opt-in emails need a verified domain before they can be sent              |
| Keep the confirmation email simple | Makes it easier for subscribers to understand and complete the confirmation step |
| Use a recognizable from address    | Reduces the chance of the confirmation email being ignored or marked as spam     |
| Monitor pending contacts           | Helps you spot low confirmation rates and improve your signup flow               |