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

# Quickstart

> Use @signal-js/node with Node.js or Express to track server events and correlate with client sessions

# Node Integration

Use **@signal-js/node** with **Node.js** or **Express** to track events on the server and correlate them with client-side sessions. Create one client with `createSignalNode()` and reuse it across requests. Pass `sessionId` and `windowId` from request headers to link server events to the same session replay.

## Quick start

1. **Install** — `npm install @signal-js/node`
2. **Initialize** — Create a client with `createSignalNode({ endpoint, apiKey, projectId })` and a helper to read `x-signal-session-id`, `x-signal-window-id`, `x-signal-distinct-id` from requests. See [Initialization](/docs/integrations/node/initialization).
3. **Track events** — Call `signal.capture()` with `sessionId` and `windowId` from the request. See [Capture](/docs/integrations/node/capture).

## Sub-pages

| Page                                                                   | Description                                           |
| ---------------------------------------------------------------------- | ----------------------------------------------------- |
| [Initialization](/docs/integrations/node/initialization)               | Install, Node.js setup, Express setup, getSessionInfo |
| [Capture](/docs/integrations/node/capture)                             | Track events with signal.capture()                    |
| [Identify](/docs/integrations/node/identify)                           | Identify users with signal.identify()                 |
| [Set person properties](/docs/integrations/node/set-person-properties) | setPersonProperties, setPersonPropertiesOnce          |
| [Group](/docs/integrations/node/group)                                 | groupIdentify, group — associate users with groups    |
| [Alias](/docs/integrations/node/alias)                                 | Link alias to user with signal.alias()                |
| [Flush and shutdown](/docs/integrations/node/flush-shutdown)           | flush(), shutdown()                                   |
| [Configuration](/docs/integrations/node/configuration)                 | createSignalNode options                              |

## How it works

1. **Client SDK** generates `sessionId` and `windowId` when initialized.
2. **Tracing headers** (when `addTracingHeaders` is enabled on the client) add these to fetch/XHR: `X-Signal-Session-Id`, `X-Signal-Window-Id`, `X-Signal-Distinct-Id`.
3. **Server** reads these headers and passes `sessionId` and `windowId` into `signal.capture()` (and other methods).
4. **Result** — Client and server events share the same identifiers and appear together in session replay.

## Best practices

1. Extract headers — Read the tracing headers from every request when you want correlation.
2. Fallback to user ID — Use `distinctId` from headers when present, otherwise your own user ID.
3. Track key events — Call `signal.capture()` for important business events.
4. One client per process — Create a single `createSignalNode()` instance and reuse it.
5. Test correlation — Confirm client and server events appear in the same session in the dashboard.