---
title: IAB TCF
description: Turn on IAB TCF in Nuxt with the c15t module's iab option, so
  visitors under an IAB policy get the IAB banner, preference centre and
  __tcfapi.
group: frameworks
lastModified: "2026-10-10T16:01:45+01:00"
---
## 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:

```ts title="nuxt.config.ts (c15t options)"
// 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](/docs/self-host/guides/iab-tcf). 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](/docs/frameworks/nuxt/troubleshooting#the-page-throws-iabunavailableerror).

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`](/docs/frameworks/nuxt/components/iab-consent-banner) and
[`IABConsentDialog`](/docs/frameworks/nuxt/components/iab-consent-dialog) 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.

```ts title="nuxt.config.ts (partial)"
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:

|`restrictionType`|Meaning|Allowed when the vendor|
|--|--|--|
|`0`|Purpose not allowed on any legal basis|declares the purpose for consent or legitimate interest|
|`1`|Consent required|declares the purpose for legitimate interest and lists it in `flexiblePurposes`|
|`2`|Legitimate interest required|declares the purpose for consent and lists it in `flexiblePurposes`|

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](/docs/concepts/consent-state#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](/docs/frameworks/nuxt/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.