---
title: Introduction
description: Get started with Plunk
---

## What is Plunk?

Plunk is an open-source email platform built on AWS SES. It provides a complete solution for transactional emails, marketing campaigns, and automated workflows—everything you need to manage email communications at scale.

## What you can build

### Send transactional emails
Send password resets, order confirmations, and notifications via API with template support and variable substitution.

```javascript
await fetch('{{API_URL}}/v1/send', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer sk_your_secret_key',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    to: 'user@example.com',
    subject: 'Welcome {{name}}!',
    body: '<h1>Hello {{name}}</h1><p>Thanks for signing up.</p>',
    data: { name: 'John' }
  })
});
```

### Run marketing campaigns
Send newsletters and product updates to segments of your audience. Schedule sends or deliver immediately.

### Automate email sequences
Build drip campaigns, onboarding flows, and behavior-triggered emails with the visual workflow builder.

## Core concepts

**Contacts** — People in your audience. Each has an email, subscription status, and custom data fields.

**Templates** — Reusable email designs. Marketing templates respect subscription status; transactional templates always send.

**Segments** — Dynamic groups based on contact data. Update automatically as data changes.

**Campaigns** — One-time email broadcasts to all contacts, a segment, or filtered audience.

**Workflows** — Automated sequences with delays, conditions, and event triggers.

**Events** — Track user actions (signups, purchases) to trigger workflows and build segments.

## Authentication

Each project has two API keys:

- **Secret Key (sk_*)** — Server-side only. Required for all endpoints except event tracking.
- **Public Key (pk_*)** — Client-side safe. Only works with `/v1/track` for event tracking.

Never expose secret keys in frontend code.

## Next steps

- [Quick Start](/getting-started/quick-start) — Send your first email in 5 minutes
- [Authentication](/getting-started/authentication) — Understand API keys
- [API Reference](/api-reference/overview) — Explore all endpoints