PostHog integration for JavaScript Node

This skill helps you add PostHog analytics to JavaScript Node applications.

Workflow

Follow these steps in order to complete the integration:

basic-integration-1.0-begin.md - PostHog Setup - Begin ← Start here
basic-integration-1.1-edit.md - PostHog Setup - Edit
basic-integration-1.2-revise.md - PostHog Setup - Revise
basic-integration-1.3-conclude.md - PostHog Setup - Conclusion

Reference files

references/node.md - Node.js - docs
references/posthog-node.md - PostHog Node.js SDK
references/identify-users.md - Identify users - docs
references/basic-integration-1.0-begin.md - PostHog setup - begin
references/basic-integration-1.1-edit.md - PostHog setup - edit
references/basic-integration-1.2-revise.md - PostHog setup - revise
references/basic-integration-1.3-conclude.md - PostHog setup - conclusion

The example project shows the target implementation pattern. Consult the documentation for API details.

Key principles

Environment variables: Always use environment variables for PostHog keys. Never hardcode them.
Minimal changes: Add PostHog code alongside existing integrations. Don't replace or restructure existing code.
Match the example: Your implementation should follow the example project's patterns as closely as possible.

Framework guidelines

posthog-node is the Node.js server-side SDK package name – do NOT use posthog-js on the server
Include enableExceptionAutocapture: true in the PostHog constructor options
Add posthog.capture() calls in route handlers for meaningful user actions – every route that creates, updates, or deletes data should track an event with contextual properties
Add posthog.captureException(err, distinctId) in the application's error handler (e.g., Express error middleware, Fastify setErrorHandler, Koa app.on('error'))
In long-running servers, the SDK batches events automatically – do NOT set flushAt or flushInterval unless you have a specific reason to
For short-lived processes (scripts, CLIs, serverless), set flushAt to 1 and flushInterval to 0 to send events immediately
Reverse proxy is NOT needed for server-side Node.js – only client-side JavaScript needs a proxy to avoid ad blockers
Remember that source code is available in the node_modules directory
Check package.json for type checking or build scripts to validate changes

Identifying users

Identify users during login and signup events. Refer to the example code and documentation for the correct identify pattern for this framework. If both frontend and backend code exist, pass the client-side session and distinct ID using X-POSTHOG-DISTINCT-ID and X-POSTHOG-SESSION-ID headers to maintain correlation.

Error tracking

Add PostHog error tracking to relevant files, particularly around critical user flows and API boundaries.