# PostHog

The c15t posthog helper runs PostHog under measurement consent in Inth. It loads PostHog opted out on each page by default, or waits for consent with loadMode: 'after-consent'.

## Key facts

- **Tool:** PostHog
- **Category:** Analytics
- **Consent categories:** Measurement
- **Setup method:** c15t package
- **Package:** @c15t/integrations

## Links

- [Documentation](https://c15t.com/docs/integrations/posthog)
- [PostHog](https://posthog.com/)

Run PostHog product analytics under measurement consent. Load it on each page opted out, or wait for consent, and turn off the modules that you do not use.

Inth keeps the consent record of each choice, with the visitor’s country and the policy that applied.

[Start for free](/dashboard/sign-up)

## Before you start

You need an Inth project that connects to your app, c15t in that app and the project token that starts with phc\_. You also need the region of your PostHog project.

New to c15t? Complete the quickstart for your framework first. Keep its Inth endpoint, policy, styles and consent UI.

[Open the quickstart for your framework](https://c15t.com/docs/frameworks)

## How consent gets to PostHog

By default, the c15t posthog helper loads array.js on each page. It calls opt\_out\_capturing() while measurement has no permission and opt\_in\_capturing() while it has permission.

The default cookieless\_mode: 'on\_reject' lets PostHog capture without cookies after a refusal. That needs cookieless server hashing in your PostHog project. Set cookieless\_mode: 'never' if a refusal must stop capture.

Use the features switches to skip surveys, heatmaps, dead clicks, Web Vitals or feature flag requests.

If your app already starts posthog-js, keep it. Register a callback-only script that calls opt\_in\_capturing and opt\_out\_capturing instead of the helper.

[Read PostHog's cookieless guide](https://posthog.com/tutorials/cookieless-tracking)

## Installation

The helper has two modes for when PostHog loads. This guide waits for permission and turns cookieless capture off.

### Wait for permission

No request goes to PostHog until the visitor accepts measurement. On withdrawal, the helper calls opt\_out\_capturing.

```ts
loadMode: 'after-consent'
```

### Load opted out

array.js loads on each page. PostHog stays opted out until the visitor accepts measurement.

```ts
loadMode: 'always'
```

An opt-out policy or no policy gives optional categories permission before a choice. Then PostHog captures on the first page. This guide uses an opt-in policy.

## Setup steps

#### Install the integration package

Add the helpers next to c15t. An import alone does not start PostHog.

```
pnpm add @c15t/integrations
```

#### Add your project token and region

The helper picks the API, UI and loader hosts from region. Set apiHost to send data through a proxy.

```
import { posthog } from '@c15t/integrations/posthog';

export const scripts = [
  posthog({
    id: 'phc_YOUR_PROJECT_TOKEN',
    region: 'eu',
    loadMode: 'after-consent',
    initOptions: { cookieless_mode: 'never' },
  }),
];
```

An empty token logs an error, and the script does not load.

### Register it with your existing setup

#### Next.js

Add scripts to c15t.config.ts, next to next.config.ts. Keep the rest of your config, such as mode, in the same call. App Router, Pages Router and static export read the same file.

```
import { defineConsentConfig } from 'c15t/next';
import { scripts } from './src/consent-scripts';

export default defineConsentConfig({ scripts });
```

#### TanStack Start

Pass scripts to the ConsentRoot in your root route. Import helpers in the route module, not in a server function: script configurations carry callbacks.

```
import { scripts } from '../consent-scripts';

<ConsentRoot state={consent} scripts={scripts}>
```

#### React

Add scripts to the options of your ConsentProvider, next to mode. Keep the banner, dialog and preferences link inside the provider.

```
import { scripts } from './consent-scripts';

<ConsentProvider options={{ mode, scripts }}>
```

#### Nuxt

Register scripts under the c15t key in app.config.ts. Keep them out of nuxt.config.ts, which reaches the browser as JSON and drops the helper callbacks.

```
import { scripts } from '../src/consent-scripts';

export default defineAppConfig({
  c15t: { scripts },
});
```

#### Vue

Pass scripts to the c15tVue plugin call you have now. The plugin starts one script loader when the app mounts.

```
import { c15tVue, manifest } from 'c15t/vue/vue-plugin';
import { scripts } from './consent-scripts';

app.use(c15tVue, {
  mode: manifest(),
  scripts,
});
```

#### Astro

Add scripts to the client entrypoint, which the integration finds on its own. Keep helpers out of astro.config.mjs: its options are serialized into the page.

```
import type { C15tClientOptionsExtension } from 'c15t/astro';
import { scripts } from './consent-scripts';

export default { scripts } satisfies C15tClientOptionsExtension;
```

#### Svelte

Pass scripts as a prop to the ConsentProvider you have now. The provider owns the loader and disposes it on unmount.

```
<script lang="ts">
  import { ConsentProvider, manifest } from 'c15t/svelte';
  import { scripts } from './consent-scripts';
</script>

<ConsentProvider mode={manifest()} {scripts}>
  <!-- Your app and consent UI -->
</ConsentProvider>
```

#### SvelteKit

Add scripts to the ConsentRoot in the root layout. Import helpers in the layout component, not in +layout.server.ts: a server load cannot send functions to the browser.

```
<script lang="ts">
  import { ConsentRoot } from 'c15t/svelte';
  import { scripts } from '../consent-scripts';

  let { children, data } = $props();
</script>

<ConsentRoot state={data.consent} {scripts}>
  {@render children()}
</ConsentRoot>
```

#### HTML: Paste the vendor’s snippet behind consent

The helpers need a bundler. On a page with the c15t script tag, paste the vendor’s own snippet instead and keep it inert until visitors allow its category. Helper options, such as loadMode, do not apply.

```
<script type="text/plain" data-c15t-category="measurement">
  // The vendor's snippet, unchanged
</script>
```

#### JavaScript

Pass scripts to init() from @c15t/browser, next to your mode. With createConsentRuntime, pass scripts to it instead.

```
import { init, manifest } from '@c15t/browser';
import { scripts } from './consent-scripts';

const consent = init({
  mode: manifest(),
  scripts,
});
```

The helper starts PostHog itself. Remove each posthog-js initializer, framework plugin or array snippet that also does.

## Verify your setup

These checks use the after-consent mode and an opt-in policy. Open a private window and DevTools Network, and filter by posthog. Then test the three states.

- **Before a choice**: array.js does not load, and no capture request goes to your API host.

- **After you allow measurement**: array.js loads, and capture requests to your API host follow. Send one guarded event and make sure that it goes out.

- **After you withdraw measurement**: Save your choice. c15t reloads the page. The new page sends no capture request.

The posthog global exists before the SDK loads. Check measurement permission before each capture call in your code, for example with useConsent('measurement') in React.

[Open the full PostHog guide](https://c15t.com/docs/integrations/posthog)

## Related guides

- [Amplitude](/integrations/amplitude)

- [Gainsight PX](/integrations/gainsight-px)

- [Heap](/integrations/heap)