PostHog Integration for Web JavaScript

---
name: integration-javascript_web
description: >-
  PostHog integration for client-side web JavaScript applications using
  posthog-js
metadata:
  author: PostHog
  version: 1.9.4
---

# PostHog integration for JavaScript Web

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

## Workflow

Follow these steps in order to complete the integration:

1. `basic-integration-1.0-begin.md` - PostHog Setup - Begin ← **Start here**
2. `basic-integration-1.1-edit.md` - PostHog Setup - Edit
3. `basic-integration-1.2-revise.md` - PostHog Setup - Revise
4. `basic-integration-1.3-conclude.md` - PostHog Setup - Conclusion

## Reference files

- `references/js.md` - JavaScript web - docs
- `references/posthog-js.md` - PostHog JavaScript web 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

- Remember that source code is available in the node_modules directory
- Check package.json for type checking or build scripts to validate changes
- posthog-js is the JavaScript SDK package name
- posthog.init() MUST be called before any other PostHog methods (capture, identify, etc.)
- posthog-js is browser-only — do NOT import it in Node.js or server-side contexts (use posthog-node instead)
- Autocapture is ON by default with posthog-js (tracks clicks, form submissions, pageviews). Do NOT disable autocapture unless the user explicitly requests it.
- NEVER send PII in posthog.capture() event properties — no emails, full names, phone numbers, physical addresses, IP addresses, or user-generated content
- PII belongs in posthog.identify() person properties (email, name, role), NOT in capture() event properties
- Call posthog.identify(userId, { email, name, role }) on login AND on page refresh if the user is already logged in
- Call posthog.reset() on logout to unlink future events from the current user
- For SPAs without a framework router, capture pageviews with posthog.capture($pageview) or use the capture_pageview history_change option in init for History API routing

## 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.