IAB TCF

Turn on IAB TCF

IAB TCF is off until you turn it on. Add iab under the c15t key in nuxt.config.ts; an empty object is enough:

// Turns IAB TCF on. The CMP ID and vendor list come from `/init`.
iab: {},

With iab set, ConsentRoot renders the IAB banner and preference centre in place of the standard ones while the visitor's policy uses the iab model and names your CMP ID, and c15t installs __tcfapi. Configure the CMP ID and vendors in your Inth project, or see IAB TCF for a self-hosted backend. No extra component or stylesheet is needed; the IAB components include their own styles.

Without iab, or with iab: false or iab: { enabled: false }, IAB stays off: no __tcfapi is installed, the app never loads @c15t/iab, and pages do not prefetch it.

If a visitor's policy uses the iab model and the backend sends its vendor list while IAB is off, the app throws an IABUnavailableError (code C15T_IAB_UNAVAILABLE). The standard banner does not handle the IAB model, so the visitor would otherwise get no working consent UI. A server render fails and Nuxt renders its error page with status 500. On a page the browser resolves itself, such as a prerendered page or one with ssr: false, the module shows the same error page from the browser. Set iab, or remove the iab model from the policy. A backend that answers gvl: null turns IAB off for the request, and the policy runs as opt-in. See troubleshooting.

Set iab in nuxt.config.ts rather than only in app.config.ts. The build reads the module options to decide whether pages prefetch the IAB banner and CMP. IAB set only in app.config.ts still works, but the browser fetches those files only once the policy calls for them, so the CMP is ready later and, on ssr: false pages, the IAB banner appears later. iab is read once, when the app starts; changing it with updateAppConfig() has no effect.

To compose the IAB surfaces yourself, import IABConsentBanner and IABConsentDialog and render them in place of ConsentRoot. For a custom preference centre, useConsentIabSelection() reads the visitor's purpose and vendor selection and useConsentIabSave() writes it and the TC String.

Restrict how vendors use a purpose

Publisher restrictions override a vendor's declared use of one purpose. Set them under the module's iab option. The vendor IDs below are placeholders; use vendors from your list whose declarations allow each restriction.

export default defineNuxtConfig({
	modules: ['c15t/vue'],
	c15t: {
		iab: {
			publisherRestrictions: [
				// Vendors 10 and 755 may not use purpose 4.
				{ purposeId: 4, restrictionType: 0, vendorIds: [10, 755] },
				// Vendor 755 must use legitimate interest for purpose 7.
				{ purposeId: 7, restrictionType: 2, vendorIds: [755] },
			],
		},
	},
});

iab also takes publisherCountryCode, a vendors allowlist, customVendors and cmpVersion. Fields you leave out come from the policy: the CMP ID, custom vendors and vendor list arrive with /init. The CMP mounts only while the visitor's policy uses the iab model.

Each restriction type has a requirement that depends on the vendor list:

Type 2 is never allowed for purposes 1, 3, 4, 5 and 6, which TCF allows only with consent. TCF allows restrictions only in service-specific TC strings. c15t always writes those, so the deprecated isServiceSpecific option has no effect on restrictions. c15t copies the restrictions when the CMP starts, so changing your array afterwards has no effect.

c15t checks restrictions when the vendor list loads and again before each TC String is encoded. Unsupported restrictions include type 3, which the spec reserves, a vendor or purpose missing from the list, and a vendor with two restriction types for one purpose. They are never dropped. Loading IAB settings, saving and generating a TC String all reject with a PublisherRestrictionError exported by @c15t/iab. On a createIAB handle these are whenReady(), save() and generateTCString(). No TC String is written and no consent is recorded. Retrying whenReady() does not fetch another vendor list. The error lasts until a new vendor list is set up: with an explicit gvl option that never happens, so saving keeps failing even if the kernel later holds a different list. When the CMP follows the kernel's list instead, a replacement list is checked again and saving works once it accepts the restrictions. When a replacement vendor list makes a restriction unsupported, c15t also clears the TC authority confirmed under the previous list, so gated scripts stop until the configuration is fixed. Whenever c15t withdraws the authority it confirmed, it also removes the TC String from the euconsent-v2 cookie and localStorage entry. Because the check reads the current vendor list, a vendor that stops declaring a purpose or its flexibility makes a restriction invalid. Narrow a vendors allowlist and your restrictions together.

Saved TC Strings carry the restrictions in their PubRestrictions section, and __tcfapi('getTCData') reports them as publisher.restrictions, keyed by purpose ID, then vendor ID. A stored TC String whose restrictions differ from the current configuration is not restored. If the visitor's stored choice is otherwise current, the banner opens again, as it does after a policy change, and closes once the visitor saves. IAB gates that depend on the TC String stay denied until then. c15t also removes the superseded TC String from the euconsent-v2 cookie and localStorage entry, so vendors reading standard storage do not pick it up. An unchanged configuration restores the stored TC String without asking. When reading a string written under TCF policy version 2 or 3, c15t accepts type 2 for purposes 3 to 6, which those versions allowed. Strings c15t writes always follow the current policy.

The React, Vue, Svelte and @c15t/browser/iab preference centres list each vendor under the legal basis the restrictions leave it. A vendor whose purpose now requires legitimate interest gets an objection control instead of a consent toggle, and a prohibited purpose no longer lists the vendor. A purpose whose vendors all use legitimate interest has no consent switch, because turning one off would change nothing the vendors rely on; its objection control is the opt-out. Such a purpose does not decide its c15t category: the category follows the purposes in it that the visitor can consent to. Legitimate interest never grants a category on its own. If none of a category's purposes has a consent basis, nothing can consent to them, Accept All included, so the category stays denied. See categories under an IAB policy. Stack switches cover only the purposes some vendor processes on consent. Display-model rows expose this as hasConsentBasis. Custom preference UIs can call applyPublisherRestrictionsToGVL from @c15t/iab/headless, or pass publisherRestrictions to processGVLForDialog, to get the same vendor declarations. The configured restrictions are on the kernel's IAB state as publisherRestrictions.

Consent-gated scripts, network rules and iframes with a vendorId also apply the confirmed restrictions for that vendor:

• Type 0 blocks a target that declares the purpose in iabPurposes or iabLegIntPurposes.
• Type 1 makes a purpose declared in iabLegIntPurposes require purpose and vendor consent. Legitimate interest no longer satisfies it.
• Type 2 makes a purpose declared in iabPurposes require purpose and vendor legitimate interest. Consent no longer satisfies it.

Types 1 and 2 block the target when the vendor list does not mark the purpose as flexible for that vendor. Targets without a vendorId ignore restrictions. A target that uses only legitimate interest once restrictions apply is not blocked by a refused category, since it needs no consent; its legitimate interest signals and the visitor's objection decide. GPC and strict scope still block it, and the category stays refused for scripts that depend on it. Accept All grants the vendor signal a restriction moves a purpose to, including legitimate interest for a vendor that declares none. Legitimate interest a restriction introduces applies until the visitor objects: the preference centres show it as allowed, and saving without touching it encodes it as allowed. introducedLegitimateInterest from @c15t/iab/headless lists those purposes and vendors for custom preference UIs.

Vendor list during server rendering

For an IAB policy, the server HTML carries the banner's purpose names, vendor count and a reference to the Global Vendor List, not the whole list. The banner renders on the server with the same summary the browser shows. After hydration, the IAB module fetches the full list and loads it before it saves a TC String. In the default manifest() mode, the module's init route serves the versioned list with a one-day public cache. Allow that route, or your backend origin, in your CSP connect-src. See Content Security Policy.

How the preference centre shows features

The stock IAB preference centres in React, Next.js, Vue, Svelte, Astro and the script tag follow TCF 2.4 and Policies v5.0.b. Special purposes stay in their locked section with a lock icon, because the visitor cannot object to them.

Features get their own section after the special purposes. It shows the IAB standard text for features from the Global Vendor List's standardTexts.features. If the list has no standard text, it shows the iab.preferenceCenter.features.description translation. Each feature lists its name, description, illustrations and the vendors that use it. The section has no switch, lock or vendor toggle, because TCF forbids showing features next to a control that cannot be disabled.

The feature section follows the theme's spacing and typography tokens. Its disclosure arrows are decorative and stay out of the accessibility tree.

A custom preference UI gets the same rows from resolveIABDialogDisplayModel in @c15t/iab/headless. essentialRows holds the special purposes only. featureRows holds the features, with locked: false and toggle: 'none', so render them without a control. featuresStandardText is the standard text, or null when you should use the translation.

Each vendor's privacy policy and legitimate interest links come from its urls[] entry in the Global Vendor List. The stock preference centres pick the entry for the language the banner shows, then English. A custom UI gets the same links from resolveIABVendorUrls(vendor, language) in @c15t/iab/headless, or from policyUrl and legitimateInterestUrl on the vendors processGVLForDialog returns when you pass it language. Vendor lists older than GVL v3 have a single policyUrl field, which c15t still reads.

Consent scope

c15t stores TCF choices per site and browser, which the TCF calls service-specific scope. It does not sync TC strings across devices, and every TC string it writes has IsServiceSpecific set to 1.

Do not use /consent/check or your own account data to skip the TCF banner on another device. That turns the choice into multi-device scope, which the TCF requires you to disclose in the first layer, and c15t does not show that disclosure. The isServiceSpecific option is deprecated. c15t ignores it and logs a warning when you pass false.

Verify IAB consent

Load a page under your IAB policy and confirm the IAB banner appears. In the browser console, __tcfapi('getTCData', 2, console.log) returns a TC String after you accept or reject. If Nuxt shows its error page with an IABUnavailableError instead, iab is not set.