Callbacks

useC15t() exposes subscribers for every consent lifecycle event. Each returns an unsubscribe function you should call when the component unmounts.

<script setup lang="ts">
const { onBannerFetched, onConsentSet, onConsentChanged, onError } = useC15t()

const stopBanner = onBannerFetched((payload) => {
  console.log('jurisdiction', payload.jurisdiction)
  console.log('location', payload.location)
})

const stopChanged = onConsentChanged((payload) => {
  console.log('granted:', payload.allowedCategories)
  console.log('denied:', payload.deniedCategories)
})

onBeforeUnmount(() => {
  stopBanner()
  stopChanged()
})
</script>

Available callbacks

Method	Fires when	Payload
onBannerFetched	The consent banner has resolved its jurisdiction and translations.	{ jurisdiction, location, translations }
onConsentSet	Consent is assigned (including automatic grants for no-jurisdiction visitors). Replays the current state on registration.	{ preferences }
onConsentChanged	An explicit save changed the previously saved state. Does not replay on registration.	{ preferences, previousPreferences, allowedCategories, deniedCategories, previousAllowedCategories, previousDeniedCategories }
onError	Any internal error — backend fetch, storage, translations.	{ error }
onBeforeConsentRevocationReload	Just before a page reload triggered by consent revocation (when reloadOnConsentRevoked is enabled). Runs synchronously.	{ preferences }

Generic on()

For ad-hoc subscriptions or dynamic event names, use the generic form:

const { on } = useC15t()

const stop = on('onConsentSet', (payload) => {
  console.log(payload.preferences)
})

Same return value — an unsubscribe function.

Single-handler rule

Each event has one slot. Registering a second handler for the same event replaces the first. If you need multiple listeners for one event, fan out inside your handler:

const listeners: Array<(p: OnConsentSetPayload) => void> = []

onConsentSet((payload) => {
  for (const fn of listeners) fn(payload)
})

When to use what

• onConsentChanged — analytics / side-effects that should only fire on a real user action. Skips hydration, auto-grants, and re-renders.
• onConsentSet — anything that needs the current consent state as soon as you subscribe, including during initialisation.
• onBannerFetched — to branch on detected jurisdiction or translate additional UI.
• onError — centralised error reporting (Sentry, internal logs).
• onBeforeConsentRevocationReload — show a loader before the reload. Keep it synchronous.