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

Adding the SDK callback to c15t

The PostHog SDK approach uses callbacks.onConsentSet instead of scripts. This lets you toggle PostHog's opt-in/opt-out based on the user's consent choice.

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';

getOrCreateConsentRuntime({
  mode: 'c15t',
  callbacks: {
    onConsentSet({ preferences }) {
      if (preferences.measurement) {
        posthog.opt_in_capturing();
      } else {
        posthog.opt_out_capturing();
      }
    },
  },
});

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',
  defaults: '2025-05-24',
  options: { person_profiles: 'identified_only' },
});

Types

PosthogConsentOptions

Property

Types

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Script

Property

Types

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PostHog

PostHog SDK Implementation

Adding the PostHog SDK to c15t

Initialize Posthog

Adding the SDK callback to c15t

PostHog Script Implementation

Initialize Posthog

Adding the script to c15t

Types

PosthogConsentOptions

apiHostYour posthog api host.requiredstring

defaultsThe defaults for the posthog script.requiredstring

idYour posthog id, begins with 'phc_'.requiredstring

optionsOther optional options for the posthog script.requiredRecord<string, unknown>

script?Override or extend the default script values. Default values: id: 'posthog-consent' category: 'measurement' Partial<Script>

Script

anonymizeId?Whether to use an anonymized ID for the script element, this helps ensure the script is not blocked by ad blockersboolean | undefined

async?Whether to use async loadingboolean | undefined

attributes?Additional attributes to add to the script elementRecord<string, string>

categoryConsent category or condition required to load this scriptrequiredHasCondition<AllConsentNames>

defer?Whether to defer script loadingboolean | undefined

fetchPriority?Priority hint for browser resource loading"high" | "low" | "auto" | undefined

iabLegIntPurposes?IAB TCF legitimate interest purpose IDs. These purposes can operate under legitimate interest instead of consent. The script loads if all iabPurposes have consent OR all iabLegIntPurposes have legitimate interest established.{} | undefined

iabPurposes?IAB TCF purpose IDs this script requires consent for. When in IAB mode and no vendorId is set, the script will only load if ALL specified purposes have consent.{} | undefined

iabSpecialFeatures?IAB TCF special feature IDs this script requires. Special features require explicit opt-in: 1: Use precise geolocation data 2: Actively scan device characteristics for identification {} | undefined

idUnique identifier for the scriptrequiredstring

nonce?Content Security Policy noncestring | undefined

onBeforeLoad?Callback executed before the script is loaded((info: ScriptCallbackInfo) => void) | u...

onConsentChange?Callback executed whenever the consent store is changed. This callback only applies to scripts already loaded.((info: ScriptCallbackInfo) => void) | u...

onError?Callback executed if the script fails to load((info: ScriptCallbackInfo) => void) | u...

onLoad?Callback executed when the script loads successfully((info: ScriptCallbackInfo) => void) | u...

persistAfterConsentRevoked?Whether the script should persist after consent is revoked.boolean | undefined

src?URL of the script to loadstring | undefined

textContent?Inline JavaScript code to executestring | undefined

vendorId?IAB TCF vendor ID - links script to a registered vendor. When in IAB mode, the script will only load if this vendor has consent. Takes precedence over category when in IAB mode. Use custom vendor IDs (string or number) to gate non-IAB vendors too.string | number | undefined

apiHostYour posthog api host.requiredstring

defaultsThe defaults for the posthog script.requiredstring

idYour posthog id, begins with 'phc_'.requiredstring

optionsOther optional options for the posthog script.requiredRecord<string, unknown>

script?Override or extend the default script values. Default values: id: 'posthog-consent' category: 'measurement' Partial<Script>

anonymizeId?Whether to use an anonymized ID for the script element, this helps ensure the script is not blocked by ad blockersboolean | undefined

async?Whether to use async loadingboolean | undefined

attributes?Additional attributes to add to the script elementRecord<string, string>

categoryConsent category or condition required to load this scriptrequiredHasCondition<AllConsentNames>

defer?Whether to defer script loadingboolean | undefined

fetchPriority?Priority hint for browser resource loading"high" | "low" | "auto" | undefined

iabLegIntPurposes?IAB TCF legitimate interest purpose IDs. These purposes can operate under legitimate interest instead of consent. The script loads if all iabPurposes have consent OR all iabLegIntPurposes have legitimate interest established.{} | undefined

iabPurposes?IAB TCF purpose IDs this script requires consent for. When in IAB mode and no vendorId is set, the script will only load if ALL specified purposes have consent.{} | undefined

iabSpecialFeatures?IAB TCF special feature IDs this script requires. Special features require explicit opt-in: 1: Use precise geolocation data 2: Actively scan device characteristics for identification {} | undefined

idUnique identifier for the scriptrequiredstring

nonce?Content Security Policy noncestring | undefined

onBeforeLoad?Callback executed before the script is loaded((info: ScriptCallbackInfo) => void) | u...

onConsentChange?Callback executed whenever the consent store is changed. This callback only applies to scripts already loaded.((info: ScriptCallbackInfo) => void) | u...

onError?Callback executed if the script fails to load((info: ScriptCallbackInfo) => void) | u...

onLoad?Callback executed when the script loads successfully((info: ScriptCallbackInfo) => void) | u...

persistAfterConsentRevoked?Whether the script should persist after consent is revoked.boolean | undefined

src?URL of the script to loadstring | undefined

textContent?Inline JavaScript code to executestring | undefined

vendorId?IAB TCF vendor ID - links script to a registered vendor. When in IAB mode, the script will only load if this vendor has consent. Takes precedence over category when in IAB mode. Use custom vendor IDs (string or number) to gate non-IAB vendors too.string | number | undefined

consentsThe current consent staterequiredRecord<AllConsentNames, boolean>

element?The script element (for load/error callbacks) Will be undefined for callback-only scriptsHTMLScriptElement

elementIdThe actual DOM element ID used (anonymized if enabled)requiredstring

error?Error information (for error callbacks)Error

hasConsentHas consentrequiredboolean

idThe original script IDrequiredstring

consentsThe current consent staterequiredRecord<AllConsentNames, boolean>

element?The script element (for load/error callbacks) Will be undefined for callback-only scriptsHTMLScriptElement

elementIdThe actual DOM element ID used (anonymized if enabled)requiredstring

error?Error information (for error callbacks)Error

hasConsentHas consentrequiredboolean

idThe original script IDrequiredstring

consentsThe current consent staterequiredRecord<AllConsentNames, boolean>

element?The script element (for load/error callbacks) Will be undefined for callback-only scriptsHTMLScriptElement

elementIdThe actual DOM element ID used (anonymized if enabled)requiredstring

error?Error information (for error callbacks)Error

hasConsentHas consentrequiredboolean

idThe original script IDrequiredstring

consentsThe current consent staterequiredRecord<AllConsentNames, boolean>

element?The script element (for load/error callbacks) Will be undefined for callback-only scriptsHTMLScriptElement

elementIdThe actual DOM element ID used (anonymized if enabled)requiredstring