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<section id="intro">
  ## What is IAB TCF?

  The [IAB Transparency & Consent Framework (TCF)](https://iabeurope.eu/tcf-2-0/) is a standardized protocol for communicating user consent choices to ad tech vendors in the programmatic advertising ecosystem. TCF 2.3 is the current version and is widely adopted across the EU/EEA.

  When your site participates in the IAB ecosystem (ad exchanges, SSPs, DSPs, DMPs), you need to:

  * Disclose which vendors process user data and for what purposes
  * Collect granular consent for each IAB-defined purpose
  * Generate a **TC String** — a standardized encoding of consent choices that ad tech vendors can read
  * Expose the `__tcfapi` CMP stub for vendor scripts to query consent status

  ## CMP Registration

  [inth.com](https://inth.com) is pending validation as an IAB Europe-registered CMP for c15t. Once approved, when you use inth.com as your backend, the correct CMP ID will be automatically provided to your client via the `/init` endpoint — no client-side configuration needed.

  If you self-host the c15t backend and have your own CMP registration with IAB Europe, you can configure your CMP ID on the backend via `advanced.iab.cmpId` or on the client via the `iab.cmpId` option. A valid (non-zero) CMP ID is required for IAB TCF compliance.

  > ℹ️ **Info:**
  > If you heavily customize or build your own IAB banner or dialog (rather than using the default IABConsentBanner and IABConsentDialog components), you cannot use inth.com's CMP ID. You must register your own CMP with IAB Europe and use your own CMP ID.

  ## How c15t Implements TCF

  c15t provides a complete IAB TCF 2.3 CMP (Consent Management Platform) implementation:

  1. **Global Vendor List (GVL)** — Automatically fetched from the c15t backend. Contains the official IAB vendor registry with purposes, features, and stacks.
  2. **IABConsentBanner** — A pre-built banner showing partner count, purpose summaries, and legitimate interest notices.
  3. **IABConsentDialog** — A tabbed preference center for granular purpose and vendor consent management.
  4. **TC String generation** — Consent choices are encoded into the standard TC String format.
  5. **`__tcfapi` stub** — The standard CMP API is exposed on `window` so vendor scripts can query consent.

  If you use the prebuilt styled IAB UI, add your framework's `iab/styles.css` entrypoint alongside the base c15t stylesheet. IAB CSS is published separately so apps that do not render IAB surfaces do not ship those component rules.
</section>

<section id="config-and-concepts">
  ## IAB Configuration Options

  Configure IAB mode with `iab({ ... })` from `@c15t/iab`. The factory enables the addon and injects the runtime module automatically. The user-facing options are:

  | Option          | Type             | Description                                                                                                                                        |
  | --------------- | ---------------- | -------------------------------------------------------------------------------------------------------------------------------------------------- |
  | `cmpId`         | `number`         | CMP ID registered with IAB Europe. Automatically provided by the backend when using inth.com. Only set this if you have your own CMP registration. |
  | `vendors`       | `number[]`       | IAB vendor IDs that your site works with                                                                                                           |
  | `customVendors` | `NonIABVendor[]` | Custom vendors not in the IAB registry                                                                                                             |

  ## Key Concepts

  ### Purposes

  IAB defines 11 standard purposes for data processing (e.g., "Store and/or access information on a device", "Select basic ads", "Measure ad performance"). Each purpose can be consented to individually.

  ### Stacks

  Purposes are grouped into **stacks** by the GVL for a simplified UI presentation. For example, "Advertising based on limited data" might group purposes 2, 7, and 10 together.

  ### Special Features

  Features like precise geolocation or device scanning that require explicit opt-in beyond standard consent.

  ### Legitimate Interest

  Some purposes can be processed under legitimate interest rather than consent. Users can object to legitimate interest processing per-vendor.

  ### Vendors

  Each vendor in the GVL declares which purposes it uses, whether via consent or legitimate interest. The preference center lets users toggle consent per-vendor.

  ## Standard vs IAB Components

  | Feature             | ConsentBanner / ConsentDialog                 | IABConsentBanner / IABConsentDialog |
  | ------------------- | --------------------------------------------- | ----------------------------------- |
  | Consent model       | opt-in / opt-out                              | IAB TCF 2.3                         |
  | Granularity         | Category-level (measurement, marketing, etc.) | Purpose-level + vendor-level        |
  | Vendor management   | No                                            | Yes (full GVL integration)          |
  | TC String           | No                                            | Yes                                 |
  | `__tcfapi`          | No                                            | Yes                                 |
  | Legitimate interest | No                                            | Yes                                 |
  | Use when            | General GDPR/CCPA compliance                  | Programmatic advertising in EU/EEA  |
</section>