PostHog

PostHog is an open-source product analytics platform that helps you understand user behavior, track events, and analyze product usage. Unlike traditional analytics tools, PostHog supports both cookieless and cookie-based tracking. This means you can sync c15t with PostHog and continue collecting analytics even when users haven't given consent—PostHog simply operates in cookieless mode until consent is granted.

PostHog SDK Implementation

This is the recommended approach if you're using the Posthog JS SDK, this is commonly used in React projects.

Adding the PostHog SDK to c15t

Initialize Posthog

When you initialize posthog make sure to set cookieless_mode to on_reject.

posthog.init('phc_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx', {
  api_host: 'https://eu.i.posthog.com',
  defaults: '2025-05-24',
  cookieless_mode: 'on_reject',
});

posthog.opt_out_capturing(); // Avoids accidental tracking without consent till c15t has loaded

The recommended PostHog SDK approach uses two phases: run one initial sync after c15t has finished resolving consent, then subscribe to future real preference changes with subscribeToConsentChanges().

Info

See the integration overview for how to wrap this in your framework (React or Next.js). Pass the callbacks option to your ConsentManagerProvider the same way you would pass scripts.

import { getOrCreateConsentRuntime } from 'c15t';
import { posthog } from 'posthog-js';

function syncPostHogMeasurementConsent(hasMeasurementConsent: boolean) {
  if (hasMeasurementConsent) {
    posthog.opt_in_capturing();
  } else {
    posthog.opt_out_capturing();
  }
}

const runtime = getOrCreateConsentRuntime({
  mode: 'hosted',
  callbacks: {
    onBannerFetched() {
      syncPostHogMeasurementConsent(
        runtime.consentStore.getState().has('measurement')
      );
    },
  },
});

runtime.consentStore
  .getState()
  .subscribeToConsentChanges(({ allowedCategories }) => {
    syncPostHogMeasurementConsent(allowedCategories.includes('measurement'));
  });

Info

Avoid using onConsentSet plus manual deduplication for PostHog. subscribeToConsentChanges() already gives you the exact change-only semantics most analytics SDKs need.

PostHog Script Implementation

If you want to load posthog via a script tag it's recommended to use this approach.

By default c15t will always load the script regardless of consent. This is because the script has built-in functionality to opt into and out of tracking based on consent.

Initialize Posthog

This script does not load the Posthog script, it only syncs the consent state with Posthog via the Posthog JS SDK.

This is due to Posthog's use of cookieless tracking. However, you need to set cookieless_mode to on_reject when initializing Posthog.

posthog.init('phc_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx', {
  api_host: 'https://eu.i.posthog.com',
  defaults: '2025-05-24',
  // PostHog will not set any cookies until the user has given consent
  cookieless_mode: 'on_reject',
});

Adding the script to c15t

Info

See the integration overview for how to pass scripts to your framework (JavaScript, React, or Next.js).

import { posthog } from '@c15t/scripts/posthog';

posthog({
  id: 'phc_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx',
  apiHost: 'https://eu.i.posthog.com',
  scriptUrl: 'https://eu-assets.i.posthog.com/static/array.js',
  initOptions: {
    api_host: 'https://eu.i.posthog.com',
    ui_host: 'https://eu.i.posthog.com',
    autocapture: false,
    person_profiles: 'identified_only',
  },
});

Types

PosthogConsentOptions

Property

Types

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Script

Property

Types

Description

Whether this is a callback-only script that doesn't need to load an external resource. When true, no script tag will be added to the DOM, only callbacks will be executed. This is useful for: Example use cases:

Full Type

boolean | undefined

Default

false

Usage

callbackOnly={...}

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PostHog

PostHog SDK Implementation

Adding the PostHog SDK to c15t

Initialize Posthog

Sync settled consent once, then subscribe to real changes

PostHog Script Implementation

Initialize Posthog

Adding the script to c15t

Types

PosthogConsentOptions

plusminusapiHost?string | undefined

plusminusidrequiredstring

plusminusinitOptions?any

plusminusscriptUrl?string | undefined

Script

plusminusalwaysLoad?boolean | undefined

plusminusanonymizeId?boolean | undefined

plusminusasync?boolean | undefined

plusminusattributes?any

plusminuscallbackOnly?boolean | undefined

plusminuscategoryrequiredHasCondition<AllCons...

plusminusdefer?boolean | undefined

plusminusfetchPriority?"high" | "low" | "au...

plusminusiabLegIntPurposes?{} | undefined

plusminusiabPurposes?{} | undefined

plusminusiabSpecialFeatures?{} | undefined

plusminusidrequiredstring

plusminusnonce?string | undefined

plusminusonBeforeLoad?((info: ScriptCallba...

plusminusonConsentChange?((info: ScriptCallba...

plusminusonError?((info: ScriptCallba...

plusminusonLoad?((info: ScriptCallba...

plusminuspersistAfterConsentRevoked?boolean | undefined

plusminussrc?string | undefined

plusminustarget?"head" | "body" | un...

plusminustextContent?string | undefined

plusminusvendorId?string | number | un...

plusminusapiHost?string | undefined

plusminusidrequiredstring

plusminusinitOptions?any

plusminusscriptUrl?string | undefined

plusminusalwaysLoad?boolean | undefined

plusminusanonymizeId?boolean | undefined

plusminusasync?boolean | undefined

plusminusattributes?any

plusminuscallbackOnly?boolean | undefined

plusminuscategoryrequiredHasCondition<AllCons...

plusminusdefer?boolean | undefined

plusminusfetchPriority?"high" | "low" | "au...

plusminusiabLegIntPurposes?{} | undefined

plusminusiabPurposes?{} | undefined

plusminusiabSpecialFeatures?{} | undefined

plusminusidrequiredstring

plusminusnonce?string | undefined

plusminusonBeforeLoad?((info: ScriptCallba...

plusminusonConsentChange?((info: ScriptCallba...

plusminusonError?((info: ScriptCallba...

plusminusonLoad?((info: ScriptCallba...

plusminuspersistAfterConsentRevoked?boolean | undefined

plusminussrc?string | undefined

plusminustarget?"head" | "body" | un...

plusminustextContent?string | undefined

plusminusvendorId?string | number | un...