Web feature flags installation

1

Install the package

Required

Install the PostHog JavaScript library using your package manager:

npm install posthog-js
yarn add posthog-js
pnpm add posthog-js

2

Initialize PostHog

Required

Import and initialize the PostHog library with your project API key and host:

JavaScript
import posthog from 'posthog-js'

posthog.init('<ph_project_api_key>', {
    api_host: 'https://us.i.posthog.com',
    defaults: '2025-11-30'
})

3
Send events
Recommended
Once installed, PostHog will automatically start capturing events. You can also manually send events to test your integration:
Click around and view a couple pages to generate some events. PostHog automatically captures pageviews, clicks, and other interactions for you.
If you'd like, you can also manually capture custom events:
JavaScript
posthog.capture('my_custom_event', { property: 'value' })

4

Next steps

Recommended

Resource	Description
Capturing events	Learn how to capture custom events beyond autocapture
Identifying users	Associate events with specific users
Creating insights	Build trends, funnels, and retention charts
Group analytics	Track events at the company or account level

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