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Instrument Product Analytics

PostHogOfficialCreated by PostHog

  • Skill
  • Tool integration
  • Data and AI
  • MIT
  • Low risk

From the author

Add PostHog product analytics events to track user behavior. Use after implementing new features or reviewing PRs to ensure meaningful user actions are captured. Also handles initial PostHog SDK setup if not yet installed.
— the description by PostHog

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a structured, multi-step workflow to integrate PostHog product analytics into a wide variety of software projects. It guides the user through detecting the project's framework, installing the appropriate SDK, initializing the service, and strategically placing event capture calls. The skill emphasizes non-intrusive implementation, requiring that new analytics code be added alongside existing logic without altering the project's fundamental architecture. It also covers user identification, error tracking, and secure environment variable management.

What it does

  • Detects the project's framework and language to determine the correct PostHog SDK.
  • Handles initial SDK installation and initialization based on framework-specific patterns.
  • Identifies key user actions and business-critical events for tracking.
  • Implements event capture calls and user identification logic.
  • Configures environment variables securely for API tokens and host URLs.
  • Verifies the integration and performs targeted linting on modified files.

When to use it

  • After implementing new features that require tracking for product analytics.
  • When reviewing pull requests to ensure meaningful user behaviors are captured.
  • During the initial setup of a new project that needs product analytics.
  • When migrating or adding analytics to an existing application.

Advantages

  • Supports a broad range of frontend, backend, and mobile frameworks.
  • Ensures consistent event naming and property usage across the codebase.
  • Prioritizes non-breaking changes and minimal impact on existing code structure.
  • Automates the complex setup of environment variables and SDK initialization.

Usage examples

“Add PostHog analytics to my Next.js project.”
The agent will analyze the project structure, install the PostHog SDK, initialize it in the appropriate client/server files, and prompt you to identify key events to track.
“I need to track user signups and errors in my Django backend.”
The agent will locate your authentication logic, add identify calls, implement exception capture, and ensure the PostHog project tokens are managed via environment variables.

Install

  1. Download the skill as a ZIP:

    https://autogineer.com/agent-skills/posthog/instrument-product-analytics/download
  2. Unzip it into the cross-client skills folder of your project:

    mkdir -p .agents/skills && unzip instrument-product-analytics.zip -d .agents/skills

Documentation by PostHog

Add PostHog product analytics events

Use this skill to add product analytics events (capture calls) that track meaningful user actions in new or changed code. Use it after implementing features or reviewing PRs to ensure key user behaviors are captured. If PostHog is not yet installed, this skill also covers initial SDK setup. Supports any framework or language.

Supported frameworks and languages: Next.js, React Router, Nuxt, Vue, TanStack Start, SvelteKit, Astro, Angular, Django, Flask, FastAPI, Laravel, PHP, Ruby on Rails, Go, Elixir, Android, iOS, Flutter, React Native, Expo, and more.

Instructions

Follow these steps IN ORDER:

STEP 1: Analyze the codebase and detect the platform.

Look for dependency files (package.json, pubspec.yaml, Podfile, Package.swift, requirements.txt, Gemfile, composer.json, go.mod, mix.exs, etc.) to determine the framework and language.

Look for lockfiles (pnpm-lock.yaml, package-lock.json, yarn.lock, bun.lockb, go.sum, pubspec.lock, Podfile.lock, Package.resolved, mix.lock) to determine the package manager.

  • Check for existing PostHog setup. If PostHog is already installed and initialized, skip to STEP 5.

STEP 2: Research integration. (Skip if PostHog is already set up.) 2.1. Find the reference file below that matches the detected framework — it is the source of truth for SDK initialization, provider setup, and event capture patterns. Read it now. 2.2. If no reference matches, fall back to your general knowledge and web search. Use posthog.com/docs as the primary search source.

STEP 3: Install the PostHog SDK. (Skip if PostHog is already set up.)

  • Add the PostHog SDK package for the detected platform. Do not manually edit package.json — use the package manager's install command.

STEP 4: Initialize PostHog. (Skip if PostHog is already set up.)

  • Follow the framework reference for where and how to initialize. This varies significantly by framework (e.g., instrumentation-client.ts for Next.js 15.3+, AppConfig.ready() for Django, create_app() for Flask).

STEP 5: Plan event tracking.

  • From the project's file list, select between 10 and 15 files that might have interesting business value for event tracking, especially conversion and churn events.

  • Also look for files related to login that could be used for identifying users, along with error handling.

  • Find any existing posthog.capture() code. Make note of event name formatting. Don't duplicate existing events; supplement them.

  • Track actions only, not pageviews (those can be captured automatically). Exceptions can be made for "viewed"-type events at the top of a conversion funnel.

  • Server-side events are REQUIRED if the project includes any instrumentable server-side code (API routes, server actions, webhook handlers, payment/checkout completion, authentication endpoints).

STEP 6: Implement event capture.

  • For each planned event, add posthog.capture() calls with useful properties.

  • If a file already has existing integration code for other tools or services, don't overwrite or remove that code. Place PostHog code below it.

  • Do not alter the fundamental architecture of existing files. Make additions minimal and targeted.

  • You must read a file immediately before attempting to write it.

STEP 7: Identify users.

  • Add PostHog identify() calls on the client side during login and signup events. Use the contents of login and signup forms to identify users on submit.

  • If both frontend and backend exist, pass the client-side session and distinct ID using X-POSTHOG-DISTINCT-ID and X-POSTHOG-SESSION-ID headers to the server-side code. On the server side, make sure events have a matching distinct ID.

STEP 8: Add error tracking.

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

STEP 9: Set up environment variables.

  • Check if the project already has PostHog environment variables configured (e.g. in .env, .env.local, or framework-specific env files). If valid values already exist, skip this step.

  • If the PostHog project token is missing, use the PostHog MCP server's projects-get tool to retrieve the project's api_token. If multiple projects are returned, ask the user which project to use. If the MCP server is not connected or not authenticated, ask the user for their PostHog project token instead.

  • For the PostHog host URL: check the projects-get MCP response for a region field — US maps to https://us.i.posthog.com, EU maps to https://eu.i.posthog.com. If the region is not available from the MCP response or from existing project configuration, ask the user: "Are you on PostHog US Cloud or EU Cloud?" Do not assume US Cloud.

  • Write these values to the appropriate env file using the framework's naming convention.

  • Reference these environment variables in code instead of hardcoding them.

STEP 10: Verify and clean up.

  • Check the project for errors. Look for type checking or build scripts in package.json.

  • Ensure any components created were actually used.

  • Run any linter or prettier-like scripts found in the package.json, but ONLY on the files you have edited or created during this session. Never run formatting or linting across the entire project's codebase.

Reference files

  • references/EXAMPLE-next-app-router.md - next-app-router example project code

  • references/EXAMPLE-next-pages-router.md - next-pages-router example project code

  • references/EXAMPLE-react-react-router-6.md - react-react-router-6 example project code

  • references/EXAMPLE-react-react-router-7-framework.md - react-react-router-7-framework example project code

  • references/EXAMPLE-react-react-router-7-data.md - react-react-router-7-data example project code

  • references/EXAMPLE-react-react-router-7-declarative.md - react-react-router-7-declarative example project code

  • references/EXAMPLE-nuxt-3-6.md - nuxt-3-6 example project code

  • references/EXAMPLE-nuxt-4.md - nuxt-4 example project code

  • references/EXAMPLE-vue-3.md - vue-3 example project code

  • references/EXAMPLE-react-tanstack-router-file-based.md - react-tanstack-router-file-based example project code

  • references/EXAMPLE-react-tanstack-router-code-based.md - react-tanstack-router-code-based example project code

  • references/EXAMPLE-tanstack-start.md - tanstack-start example project code

  • references/EXAMPLE-sveltekit.md - sveltekit example project code

  • references/EXAMPLE-astro-static.md - astro-static example project code

  • references/EXAMPLE-astro-view-transitions.md - astro-view-transitions example project code

  • references/EXAMPLE-astro-ssr.md - astro-ssr example project code

  • references/EXAMPLE-astro-hybrid.md - astro-hybrid example project code

  • references/EXAMPLE-angular.md - angular example project code

  • references/EXAMPLE-django.md - django example project code

  • references/EXAMPLE-flask.md - flask example project code

  • references/EXAMPLE-fastapi.md - fastapi example project code

  • references/EXAMPLE-python.md - python example project code

  • references/EXAMPLE-laravel.md - laravel example project code

  • references/EXAMPLE-php.md - php example project code

  • references/EXAMPLE-ruby-on-rails.md - ruby-on-rails example project code

  • references/EXAMPLE-ruby.md - ruby example project code

  • references/EXAMPLE-android.md - android example project code

  • references/EXAMPLE-swift.md - swift example project code

  • references/EXAMPLE-react-native.md - react-native example project code

  • references/EXAMPLE-expo.md - expo example project code

  • references/next-js.md - Next.js

  • references/react-router-v6.md - React router v6

  • references/react-router-v7-framework-mode.md - React router v7 framework mode (remix v3)

  • references/react-router-v7-data-mode.md - React router v7 data mode

  • references/react-router-v7-declarative-mode.md - React router v7 declarative mode

  • references/nuxt-js-3-6.md - Nuxt.js (v3.0 to v3.6)

  • references/nuxt-js.md - Nuxt.js

  • references/vue-js.md - Vue.js

  • references/tanstack-start.md - Tanstack start

  • references/svelte.md - Svelte

  • references/astro.md - Astro

  • references/angular.md - Angular

  • references/django.md - Django

  • references/flask.md - Flask

  • references/python.md - Python

  • references/posthog-python.md - PostHog python SDK

  • references/dotnet.md - .net

  • references/elixir.md - Elixir

  • references/go.md - Go

  • references/laravel.md - Laravel

  • references/php.md - Php

  • references/ruby-on-rails.md - Ruby on rails

  • references/ruby.md - Ruby

  • references/android.md - Android

  • references/ios.md - Ios

  • references/usage.md - Ios SDK usage

  • references/configuration.md - Ios SDK configuration

  • references/flutter.md - Flutter

  • references/react-native.md - React native

  • references/identify-users.md - Identify users

  • references/COMMANDMENTS.md - Framework-specific rules the integration must follow

Each framework reference contains SDK-specific installation, initialization, and usage patterns. Find the one matching the user's stack.

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 docs: Follow the framework reference's initialization and capture patterns exactly.

Files

references/astro.md

AI agents: this is one page from PostHog's docs. Full index of Markdown docs for LLMs: https://posthog.com/llms.txt

Astro

Canonical URL: https://posthog.com/docs/libraries/astro

Cloud region: This page uses US Cloud hosts. For an EU Cloud project, use https://eu.i.posthog.com instead of https://us.i.posthog.com (ingestion host), and use https://eu.posthog.com instead of https://us.posthog.com (app host for links).

On this page

  • Install with the wizard

  • Installation

  • Node.js server context and traces

  • Identifying users

  • Next steps

PostHog makes it easy to get data about traffic and usage of your Astro app. Integrating PostHog into your site enables analytics about user behavior, custom events capture, session recordings, feature flags, and more.

This guide walks you through integrating PostHog into your Astro app using the JavaScript Web SDK.

Install with the wizard

Run this command in your project directory to add PostHog to your Astro project. The wizard detects your framework, installs the SDK, and sets up your first events.

npx @posthog/wizard

Or set it up manually by following the rest of this guide.

Installation

In your src/components folder, create a posthog.astro file:

cd ./src/components
# or 'cd ./src && mkdir components && cd ./components' if your components folder doesn't exist
touch posthog.astro

In this file, add your Web snippet which you can find in your project settings. Be sure to include the is:inline directive to prevent Astro from processing it, or you will get Typescript and build errors that property 'posthog' does not exist on type 'Window & typeof globalThis'.

posthog.astro

---
// src/components/posthog.astro
---
<script is:inline>
  !function(t,e){var o,n,p,r;e.__SV||(window.posthog=e,e._i=[],e.init=function(i,s,a){function g(t,e){var o=e.split(".");2==o.length&&(t=t[o[0]],e=o[1]),t[e]=function(){t.push([e].concat(Array.prototype.slice.call(arguments,0)))}}(p=t.createElement("script")).type="text/javascript",p.crossOrigin="anonymous",p.async=!0,p.src=s.api_host+"/static/array.js",(r=t.getElementsByTagName("script")[0]).parentNode.insertBefore(p,r);var u=e;for(void 0!==a?u=e[a]=[]:a="posthog",u.people=u.people||[],Object.defineProperty(u,"toString",{configurable:!0,enumerable:!0,writable:!0,value:function(t){var e="posthog";return"posthog"!==a&&(e+="."+a),t||(e+=" (stub)"),e}}),Object.defineProperty(u.people,"toString",{configurable:!0,enumerable:!0,writable:!0,value:function(){return u.toString(1)+".people (stub)"}}),o="capture identify alias people.set people.set_once set_config register register_once unregister opt_out_capturing has_opted_out_capturing opt_in_capturing reset isFeatureEnabled onFeatureFlags getFeatureFlag getFeatureFlagResult reloadFeatureFlags group updateEarlyAccessFeatureEnrollment getEarlyAccessFeatures getActiveMatchingSurveys getSurveys getNextSurveyStep onSessionId".split(" "),n=0;n<o.length;n++)g(u,o[n]);e._i.push([i,s,a])},e.__SV=1)}(document,window.posthog||[]);
  posthog.init('<ph_project_token>', {
    api_host:'https://us.i.posthog.com',
    defaults: '2026-08-30'
  })
</script>

If your site sets a Content-Security-Policy, it needs to allow PostHog. This applies to the snippet and to package installs alike: the SDK lazy-loads extra bundles (session replay, surveys) from PostHog's CDN, and sends events to the ingestion host. PostHog serves from subdomains of posthog.com that change over time, so allow the wildcard:

script-src 'self' https://*.posthog.com;
connect-src 'self' https://*.posthog.com;
worker-src 'self' blob: data:;

script-src covers the snippet and the lazy-loaded bundles, connect-src covers event ingestion and feature flags, and worker-src covers session replay. The toolbar needs a few more, or use a reverse proxy so everything is first-party. Failing to do so causes silent failures where capture and identify calls never send, so the integration looks complete while zero events arrive. Remember connect-src falls back to default-src, so default-src 'self' blocks event delivery even when the script itself is bundled.

Using with Astro's view transitions (ClientRouter)

If you've opted in to Astro's <ClientRouter> component for client-side navigation, you'll need to add an initialization guard to prevent PostHog from running multiple times during page transitions.

Update your posthog.astro file to wrap the snippet with a check:

posthog.astro

---
// src/components/posthog.astro
---
<script is:inline>
  if (!window.__posthog_initialized) {
    window.__posthog_initialized = true;

    !function(t,e){var o,n,p,r;e.__SV||(window.posthog=e,e._i=[],e.init=function(i,s,a){function g(t,e){var o=e.split(".");2==o.length&&(t=t[o[0]],e=o[1]),t[e]=function(){t.push([e].concat(Array.prototype.slice.call(arguments,0)))}}(p=t.createElement("script")).type="text/javascript",p.crossOrigin="anonymous",p.async=!0,p.src=s.api_host+"/static/array.js",(r=t.getElementsByTagName("script")[0]).parentNode.insertBefore(p,r);var u=e;for(void 0!==a?u=e[a]=[]:a="posthog",u.people=u.people||[],Object.defineProperty(u,"toString",{configurable:!0,enumerable:!0,writable:!0,value:function(t){var e="posthog";return"posthog"!==a&&(e+="."+a),t||(e+=" (stub)"),e}}),Object.defineProperty(u.people,"toString",{configurable:!0,enumerable:!0,writable:!0,value:function(){return u.toString(1)+".people (stub)"}}),o="capture identify alias people.set people.set_once set_config register register_once unregister opt_out_capturing has_opted_out_capturing opt_in_capturing reset isFeatureEnabled onFeatureFlags getFeatureFlag getFeatureFlagResult reloadFeatureFlags group updateEarlyAccessFeatureEnrollment getEarlyAccessFeatures getActiveMatchingSurveys getSurveys getNextSurveyStep onSessionId".split(" "),n=0;n<o.length;n++)g(u,o[n]);e._i.push([i,s,a])},e.__SV=1)}(document,window.posthog||[]);

    posthog.init('<ph_project_token>', {
      api_host: 'https://us.i.posthog.com',
      defaults: '2026-08-30',
      capture_pageview: 'history_change'
    })
  }
</script>

Without this guard, ClientRouter's soft navigation can re-execute the inline script during page transitions, causing a stack overflow error. The capture_pageview: 'history_change' option ensures pageviews are tracked automatically as users navigate.

The next step is to a create a Layout where we will use posthog.astro. Create a new file PostHogLayout.astro in your src/layouts folder:

cd .. && cd .. # move back to your base directory if you're still in src/components/posthog.astro
cd ./src/layouts
# or 'cd ./src && mkdir layouts && cd ./layouts' if your layouts folder doesn't exist yet
touch PostHogLayout.astro

Add the following code to PostHogLayout.astro:

PostHogLayout.astro

---
import PostHog from '../components/posthog.astro'
---
<head>
    <PostHog />
</head>

Lastly, update index.astro to wrap your existing app components with the new Layout:

index.astro

---
import PostHogLayout from '../layouts/PostHogLayout.astro';
---
<PostHogLayout>
  <!-- your existing app components -->
</PostHogLayout>

Node.js server context and traces

For on-demand rendering with @astrojs/node in middleware mode, use the shared Node SDK on your Express server. The browser setup above does not add server context.

Reuse one server posthog-node client. Add PostHogContextSpanProcessor from posthog-node/otel to your application's existing OpenTelemetry provider. Keep your exporter, sampler, and other processors. Load your tracing setup, including HTTP and Express instrumentation, before importing the server modules below.

Configure the Node adapter for middleware mode:

import { defineConfig } from 'astro/config'
import node from '@astrojs/node'

export default defineConfig({
    output: 'server',
    adapter: node({ mode: 'middleware' }),
})

Place the request middleware before the generated Astro handler. Pass the same client through the adapter's public locals argument so pages, endpoints, actions, and Astro middleware can reuse it:

import express from 'express'
import { handler as ssrHandler } from './dist/server/entry.mjs'
import { setupExpressRequestContext } from 'posthog-node'
import posthog from './posthog.server.mjs'

const app = express()
app.use(express.static('dist/client'))
setupExpressRequestContext(posthog, app)
app.use((req, res, next) => ssrHandler(req, res, next, { posthog }))
app.listen(4321)

The middleware reads PostHog tracing headers. An existing application identity takes precedence over the browser fallback. The headers are untrusted analytics context and must not be used for authentication or authorization. Only requests that carry the headers receive browser IDs; standard browser document navigations do not gain fetch/XHR-added tracing headers.

The optional processor adds sessionId and posthogDistinctId to recording application spans. Explicit canonical attributes keep their values. At request entry, it also fills missing IDs on the nearest recording HTTP server ancestor through parent objects it has observed. A sampler-dropped intermediate span breaks that verified chain, so the earlier server span stays unchanged. New recording spans inside the request still receive context.

Express owns the request context. It stays active for work that the request starts, including while a response body streams and after the response ends. A background job that needs its own IDs must use a new explicit context.

Astro can handle errors before they reach Express's error middleware. To capture errors thrown by next(), use the same client from your existing Astro middleware chain:

import { defineMiddleware } from 'astro:middleware'

export const onRequest = defineMiddleware(async ({ locals }, next) => {
    try {
        return await next()
    } catch (error) {
        locals.posthog.captureException(error)
        throw error
    }
})

Keep your other middleware when adding error capture. Capture errors from later streaming work where they occur, because next() may already have returned.

This setup covers the Node adapter's middleware mode. Prerendered pages and static assets use the browser integration; standalone and edge deployments need their own verified context and response lifetime setup. See Astro's Node adapter guide and the Node.js tracing guide.

Identifying users

Identifying users is required. Call posthog.identify('your-user-id') after login to link events to a known user. This is what connects frontend event captures, session replays, LLM traces, and error tracking to the same person — and lets backend events link back too.

Use a stable ID from your auth system when possible, not an email or display name. Send those as person properties instead. If your app has no other stable key, email works as a fallback if they are unique. Never a shared literal like "anonymous" or "user", which pools many people onto one person and corrupts their data. When no ID is available at all, skip the identify and retain the anonymous distinct ID that's automatically assigned.

Call posthog.reset() on logout, so the next person to use the browser doesn't inherit the last one's identity.

See our guide on identifying users for how to set this up.

If your app calls your own backend, tracing_headers adds X-POSTHOG-DISTINCT-ID and X-POSTHOG-SESSION-ID to matching fetch and XMLHttpRequest requests. This lets server-side SDKs link backend events, errors, and LLM traces back to frontend sessions and replays. Use hostnames only, without protocols or paths.

posthog.init('<ph_project_token>', {
  api_host: 'https://us.i.posthog.com',
  // Optional: send PostHog session/user context to your backend
  tracing_headers: ['api.example.com'],
})

This works in local development too, but match on the hostname alone: use 'localhost', not 'localhost:3000'. Ports are never part of a hostname, so a value with one in it never matches anything. localhost and 127.0.0.1 are also different hostnames — use whichever your app actually calls.

Tracing headers help you attribute events across front and backend consistently. When this isn't available, use your server-side stable IDs to deduce the matching distinctId, and pass it in when capturing the event.

Set up a reverse proxy (recommended)

We recommend setting up a reverse proxy, so that events are less likely to be intercepted by tracking blockers.

We have our own managed reverse proxy service, which is free for all PostHog Cloud users, routes through our infrastructure, and makes setting up your proxy easy.

If you don't want to use our managed service then there are several other options for creating a reverse proxy, including using Cloudflare, AWS Cloudfront, and Vercel.

Grouping products in one project (recommended)

If you have multiple customer-facing products (e.g. a marketing website + mobile app + web app), it's best to install PostHog on them all and group them in one project.

This makes it possible to track users across their entire journey (e.g. from visiting your marketing website to signing up for your product), or how they use your product across multiple platforms.

Add IPs to Firewall/WAF allowlists (recommended)

For certain features like heatmaps, your Web Application Firewall (WAF) may be blocking PostHog's requests to your site. Add these IP addresses to your WAF allowlist or rules to let PostHog access your site.

EU: 3.75.65.221, 18.197.246.42, 3.120.223.253

US: 44.205.89.55, 52.4.194.122, 44.208.188.173

These are public, stable IPs used by PostHog services.

PostHog captures heatmap screenshots using Browserless, which has its own IP addresses. Browserless publishes the current list here.

An allowlist does not help when your app has a private address. For apps on an internal network, see internal and intranet applications.

Next steps

For any technical questions for how to integrate specific PostHog features into Astro (such as analytics, feature flags, A/B testing, surveys, etc.), have a look at our JavaScript Web SDK docs.

Alternatively, the following tutorials can help you get started:

Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs an MCP server, Needs Python, Needs Node.js

Security

What our scanner noticed· Low risk

  • Instructions that use the network

A static scan is not a guarantee. Skills are third-party content: review a skill before you let an agent use it.

Attribution and licence

Created by
PostHog
Publisher
PostHog (Official)
Source
PostHog/skills · skills/omnibus/instrument-product-analytics · commit a5d30e7
Licence
MIT License (redistribution allowed)
  • LICENSE (added by AutoGineer from LICENSE)
  • ATTRIBUTION.md (written by AutoGineer)
Synced

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