CMP - TCF 2.3 Instructions

Overview

Under GDPR, publishers must obtain user consent in the EEA (European Economic Area) and UK before personal data can be processed for advertising.  The IAB Europe Transparency & Consent Framework (TCF) standardizes how consent signals are passed to vendors.

IAB Europe is upgrading from TCF v2.2 to v2.3, with mandatory compliance required by:  February 28, 2026.  If your CMP is not TCF 2.3 compliant after this date, EU / EEA / UK traffic will not monetize.

What Changed in TCF 2.3?

The primary update is the introduction of a required “Disclosed Vendors” segment in the TC string.

Under TCF v2.3:

• Vendors must be explicitly disclosed in this segment

• If a vendor is not disclosed, consent signals cannot be transmitted to that vendor

• No consent signal = no ad serving

---

Required Configuration for Underdog Media 

To ensure continued monetization:

1. Use a TCF 2.3-Compliant CMP

   Confirm your CMP has upgraded to TCF 2.3.  
   Your CMP must be:

   1. IAB Authorized (TCF registered)

   2. Properly implemented on all domains

   3. Actively generating valid TC strings

2. Enable Underdog Media 

   Search for:  Underdog Media LLC, Vendor ID: 159

   This vendor must be included in your CMP’s Disclosed Vendors list.

3. Enable Automatic Vendor Disclosure

   If your CMP provides an option to automatically disclose all registered IAB vendor IDs, enable this setting.

   Why? - Underdog Media works with downstream demand partners who must also receive consent signals in order to bid. Automatic disclosure helps prevent revenue loss caused by incomplete vendor selection.

4. Or, if Your CMP Does Not Support Automatic Vendor Disclosure

   You must manually select:

   1. Underdog Media (Vendor ID 159) AND our downstream demand partners.

   2. Downstream demand partners are available on this list.

      Failure to disclose required vendors will result in lower fill rates and reduced monetization

---

CMP Settings Recommendations

CMPs differ by provider, but we recommend:

• Enable all available purposes where appropriate

• At minimum, enable Purpose 4 (Personalized Ads / Targeting)

Important:  Underdog Media is not a Legitimate Interest vendor.  User consent is required.

How to Test Your Implementation

After updating your CMP:

1. Use a VPN to load your site in an EU geolocation

2. Accept consent

3. Copy the generated TC string

4. Use a TCF string decoder, browser developer tools or your CMP’s built-in validator to confirm that:

• The TC string includes a Vendors Disclosed segment with Underdog Media's vendor ID 159 enabled

• The TC string includes Vendor Consent with Underdog Media's vendor ID: 159

Google Verification: If using Google monetization products, confirm that Syn Technologies LLC is properly declared in your ATP settings and that no warnings or transparency errors appear in Google Ad Manager.

CMP Recommendation (If You Don’t Have One)

There are many CMP options available. Choose one that fits your business and is:

• IAB TCF authorized

• Google-certified (required if using Google demand)

If you do not currently have a CMP, one easy option is InMobi Choice CMP. Free trials are available and setup is quick (≈10 minutes).

GDPR Compliance Resources

• List of Consent Management Platforms
• List of Vendors
• Google Consent Tool, “Funding Choices”

• Google Vendor List

Impact of Non-Compliance

If your CMP is not TCF 2.3 compliant by February 28, 2026, EU / EEA / UK traffic will not monetize.

Need Help?

If you’d like us to review your CMP configuration or test your implementation, email [e-mail].

We’re happy to help ensure everything is configured properly before the deadline.