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

# Installation

> Pick your integration method and start sending events in minutes.

There are three ways to get events into Retain, and you only need one of them.

Use the **Node.js SDK** if you are on Node. Use the **HTTP API** from any other language, with nothing to install. Or, if you already track product usage in a tool like PostHog, **connect that tool** and skip instrumentation entirely.

## Node.js

Install the SDK with your preferred package manager.

**Requirements:** Node.js 20 or later.

<CodeGroup>
  ```bash npm theme={"theme":"vesper"}
  npm install @retain-so/sdk
  ```

  ```bash pnpm theme={"theme":"vesper"}
  pnpm add @retain-so/sdk
  ```

  ```bash yarn theme={"theme":"vesper"}
  yarn add @retain-so/sdk
  ```

  ```bash bun theme={"theme":"vesper"}
  bun add @retain-so/sdk
  ```
</CodeGroup>

Continue the Quickstart with [Authentication](/docs/guides/authentication), then [Identify](/docs/guides/identify) and [Track](/docs/guides/track).

## Other languages

You don’t need to install anything

Just grab your Project Token in [Authentication](/docs/guides/authentication) then move on to [Identify](/docs/guides/identify) and [Track](/docs/guides/track) for HTTP examples in your language.

If you need more details, check the [API reference](/docs/api-reference/introduction).

<Note>Official SDKs for other languages are coming soon.</Note>

## Already tracking with a product analytics tool

If your product events already flow into PostHog, you do not need to instrument anything a second time. Point a PostHog realtime destination at Retain and the events you already collect start arriving, usually in a couple of minutes.

See [Connect PostHog](/docs/guides/connect-posthog) for the full setup.

<Note>Mixpanel and Amplitude are coming soon.</Note>

## Next steps

<CardGroup cols={2}>
  <Card title="Authentication" icon="key" href="/docs/guides/authentication">
    Get your Project Token and use it from the SDK or HTTP client.
  </Card>

  <Card title="Connect PostHog" icon="plug" href="/docs/guides/connect-posthog">
    Forward the events you already track, no re-instrumentation needed.
  </Card>

  <Card title="Identify" icon="user" href="/docs/guides/identify">
    Register users in Retain before tracking events.
  </Card>

  <Card title="Track" icon="chart-line" href="/docs/guides/track">
    Record events as they happen in your product.
  </Card>
</CardGroup>