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:

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/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.