Svelte Consent API

Callbacks

Pick the right callback

Run your own code when consent changes through the provider's callbacks prop, a script's own callbacks, or a kernel event in one component:

You want to	Use
Send a choice to your analytics or CRM when the visitor makes one	`callbacks.onChoiceRecorded`
Start or stop your own code when what may run changes	`callbacks.onPermissionsChanged`
Report failed backend requests	`callbacks.onError`
Show a message or flush data before a withdrawal reloads the page	`callbacks.onBeforeConsentRevocationReload`
Call a vendor's own consent API after its script loads	The script's `onConsentChange`
React to consent inside one component	`getConsentKernel().events.on()` or the manager's properties

onChoiceRecorded or onPermissionsChanged

onChoiceRecorded runs only when the visitor accepts, rejects or saves. onPermissionsChanged runs whenever effective permissions change, whatever the cause:

Event	`onChoiceRecorded`	`onPermissionsChanged`
Visitor accepts, rejects or saves	Yes	Yes, if a permission changed
Policy resolves under opt-out and allows categories before a choice	No	Yes
Global Privacy Control overrides a grant	No	Yes
A recorded choice expires	No	Yes
Visitor dismisses a notice	No	No

Use onChoiceRecorded for consent records and audit trails, because it fires only for a visitor's action. Use onPermissionsChanged to start or stop code, because it covers every way a permission changes. Never treat onPermissionsChanged as proof that the visitor agreed to something.

Pass callbacks to the provider

src/lib/consent-callbacks.ts

import type { ConsentProviderCallbacks } from '@c15t/svelte';

// Pass as `callbacks={callbacks}` on ConsentProvider.
export const callbacks: ConsentProviderCallbacks = {
	// Runs just before c15t reloads the page after a withdrawal.
	onBeforeConsentRevocationReload: ({ preferences }) => {
		console.info('Reloading with', preferences);
	},
	// An explicit accept, reject or save. Never runs for defaults, expiry,
	// policy changes or privacy signals.
	onChoiceRecorded: ({ snapshot, confirmed }) => {
		console.info('Visitor chose', snapshot.explicitChoice, confirmed);
	},
	// A failed command, such as an /init request that could not reach the
	// backend.
	onError: ({ error }) => {
		console.warn('c15t error', error);
	},
	// Any change to what may run, whatever caused it.
	onPermissionsChanged: ({ snapshot, previous }) => {
		console.info('Permissions', previous, '->', snapshot.effectivePermissions);
	},
};

Pass the object as callbacks={callbacks} on ConsentProvider. The provider reads it once, when it is created. Keep the functions in a module or in the component that renders the provider; on SvelteKit, not in a server load, because a load cannot send functions to the browser.

Callback	Payload
`onChoiceRecorded`	`snapshot`, the state after the choice; `confirmed`, the categories this action recorded; `actionAt`, the time.
`onPermissionsChanged`	`snapshot`, the state after the change; `previous`, the permissions before it.
`onError`	`error`, a message string.
`onBeforeConsentRevocationReload`	`preferences`, the permissions after the withdrawal.

Callbacks run after c15t updates its own state, so snapshot and getConsentManager() already hold the new values. Visitor actions happen in the browser, so in practice that is where the callbacks run.

onBeforeConsentRevocationReload runs synchronously right before the reload. Keep it short; the page is about to unload. It does not run when you set reloadOnConsentRevoked={false}.

Script callbacks

Each entry in scripts takes its own callbacks:

Callback	Runs
`onBeforeLoad`	Before the loader adds the script.
`onLoad`	When the script loaded.
`onError`	When the script failed to load.
`onConsentChange`	When consent changes after the script loaded. Use it to call the vendor's own consent API.
`onDispose`	When the configuration is removed or the provider unmounts.

Helpers from @c15t/integrations already set these for their vendor. Building integrations shows how to write them.

Listen inside one component

For a component that shows or reacts to consent, subscribe to a kernel event in $effect, so the listener goes away with the component. The context getters page has the example. For values you render, read the manager's properties instead; they update the component without a listener.

Verify the callbacks

Open the console, clear site data and reload:

Accept in the banner. onChoiceRecorded and onPermissionsChanged both log.
Dismiss a notice, if your policy shows one. Neither logs.
Withdraw a category you allowed. onBeforeConsentRevocationReload logs, then the page reloads.