Laptop with a browser open on a website with Snigel CMP Consent Management Platform (to serve ads without user consent)

How to Choose a CMP (Consent Management Platform)

What are the pros and cons to using a Consent Management Platform? How do they work? Which CMPs should you choose for your website? This guide will show you how to choose a Consent Management Platform.

Why are publishers using CMPs?

A CMP helps website owners comply with data privacy laws by collecting user consent. By gathering consent, website owners are able to serve personalized ads based on the user’s data and cookies.

When a user visits a website a CMP popup or modal will ask the user to select:

  • How they would like their data to be used
  • Which organizations can use their data
browser open on a website with Snigel CMP Consent Management Platform (to serve ads without user consent)

When the user submits the form a consent string is created. This informs the publisher and third party vendors what the user’s choices were and enables these organisations to configure their services correctly. The consent string also allows SSPs and ad demand partners to serve targeted ads based on the user’s interests.

What happens when you use a CMP?

First, you’ll be compliant, so you can forget about those big fines. But that’s not the end of it. There are many pros and cons to using a CMP. Let’s cover the bad stuff first.

Enabling a CMP is going to increase your bounce rate. Publishers can expect a 10%-20% bounce rate depending on how strong the user’s intent is when visiting the site. In addition, some users will not provide consent for their data to be used. Publishers can expect an opt out rate of approximately 5-10%, however certain niche content may see higher opt-out rates. This has a negative impact on revenue but it’s not all bad news.

Publishers that collect consent with a CMP will be cleared to show personalized ads. Advertisers pay a higher price for these ads because of their enhanced targeting. This increases revenue.

Overall, publishers should expect a small decline in revenue when switching to a CMP.

What happens if you don’t use a CMP?

Besides the risk of large fines, publishers without a CMP will likely see a decline in ad demand going forward. Demand partners like Google are increasingly requesting consent strings before filling ad requests. If a publisher fails to capture user consent they should expect:

  • Significantly reduced fill rate from advertising demand partners – applicable to both personalized and non-personalized ads.
  • The non-delivery of ads from certain demand partners – Google has flagged that, “if consent is missing for Google for Purpose 1 in the TC string, Google will drop the ad request and no ads will be served.”

Does a CMP only show up for EU users?

CMPs can be configured to only pop up for users in relevant countries. For example, a CMP can be set to cover users in Geos affected by the EU’s GDPR.

We’ve outlined the positives and negatives. Our recommendation to publishers is to become compliant and adopt a CMP.

Laptop with a browser open on a website with Snigel CMP Consent Management Platform (to serve ads without user consent)

How to choose the right CMP for your site

The compliance landscape is evolving rapidly. To ensure your site stays up to date with the latest changes it’s best to find an experienced CMP provider that issues regular updates. It’s also best to work with a provider that creates CMPs specifically for websites that rely on advertising revenue. Many large CMP providers instead focus on building CMP’s for the corporate market or a wide range of website owners. We’ll cover the differences below.

IAB Approval

The interactive advertising bureau (IAB) is the authoritative body for setting online advertising standards in the US and Europe. You can find the list of approved CMP providers here. By selecting an IAB approved CMP you can be sure you are correctly gathering user consent.


The IAB has limited the CMP’s customization options to avoid confusing users. It is therefore vital that publishers use the customization options available to personalize the CMP with their logo and colour scheme. This helps reassure users that they are on the desired site. Many CMP providers offer free generic CMPs that can’t be customized. Using a generic CMP without any level of customization will likely lead to an increase in your bounce rate.

Popup frequency

As mentioned above, publishers should expect a 10%-20% bounce rate when using a CMP. Therefore, it is best to show the CMP as infrequently as possible.

Consent can legally be stored for up to 13-months. However, consent needs to be re-obtained when the publisher starts using a new vendor from the IAB’s Global Vendor List (GVL). Most CMPs re-request consent from users every time any changes are made to the GVL. This leads to needless lost revenue.

Snigel’s AdConsent CMP only re-requests consent if a publisher is affected by the GVL update. By doing this, we’re able to minimize the number of times the CMP is shown to users and the subsequent bounce rate.

Filling impressions without consent for Purpose 1

Google has stated it will not fill the ad request if a user rejects consent for Purpose 1. See “Requirements: Personalized & Non-Personalized Ads”.

If you’re only using Google demand you can expect these impressions to go unfilled. However, if you’re using header bidding or if you switch header bidding there is a solution to this problem. By connecting your website to other ad exchanges and SSPs that don’t require consent for Purpose 1, you can still fill the impression. Contact us to find out how Snigel’s AdEngine header bidding solution can do this for your site.

Consent Management Platform popup size

The IAB requires CMPs to take over a significant portion of the user’s screen when they pop up. It is essential that the website is still visible underneath the CMP. Otherwise, users will not be drawn towards the page they tried to access. Failure to correctly configure this will lead to an increase in your bounce rate.

Consent Management Platform loading speed

A fast CMP provides a smooth user experience and makes gathering consent more frictionless. Snigel’s AdConsent CMP is localised server-side and delivered on-demand, leading to minimal requests and payload.


Digital privacy will continue to be a prime concern for lawmakers going forward. Publishers should expect increased security as a result. Our recommendation is to adopt a CMP in order to avoid fines and reduced fill rates from major demand partners like Google.

Snigel’s AdConsent CMP is purpose-built for publishers that rely on ad revenue. It’s IAB approved and TCF2.0 compatible. To find out if you’re ready for TCF 2.0 check out our guide here. If you’d like to find out more about how we can minimize your bounce rate and lost revenue get in touch here.

About the Author

Ben is one of Snigel's Co-CEO. He works on business development and marketing - spreading the word about how Snigel can help publishers supercharge their ad revenue.


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