Facebook pixels cookie consent. How do I enable prior consent on a Facebook pixel?

Applying Mark Up

A Facebook Pixel consists of 2 parts:

1. The ordinary script tag that should be marked up as described in the manual mark up guide.
2. The <noscript> tag that should be removed completely

An example of how the ordinary Facebook pixel script tag may look. 

<!-- Facebook Pixel Code -->
<script>
    !function(f,b,e,v,n,t,s)
    {if(f.fbq)return;n=f.fbq=function(){n.callMethod?
    n.callMethod.apply(n,arguments):n.queue.push(arguments)};
    if(!f._fbq)f._fbq=n;n.push=n;n.loaded=!0;n.version='2.0';
    n.queue=[];t=b.createElement(e);t.async=!0;
    t.src=v;s=b.getElementsByTagName(e)[0];
    s.parentNode.insertBefore(t,s)}(window, document,'script',
    'https://connect.facebook.net/en_US/fbevents.js');
    fbq('init', '{your-pixel-id-goes-here}');
    fbq('track', 'PageView');
</script>
<noscript>
    <img height="1" width="1" style="display:none"
         src="https://www.facebook.com/tr?id={your-pixel-id-goes-here}&ev=PageView&noscript=1"/>
</noscript>
<!-- End Facebook Pixel Code -->

Below is how the script should look to enable prior consent.
Note the added mark-up (in bold) and the removal of the <noscript> tags:

<!-- Facebook Pixel Code -->
<script type="text/plain" data-cookieconsent="marketing">
    !function(f,b,e,v,n,t,s) 
    {if(f.fbq)return;n=f.fbq=function(){n.callMethod?
    n.callMethod.apply(n,arguments):n.queue.push(arguments)};
    if(!f._fbq)f._fbq=n;n.push=n;n.loaded=!0;n.version='2.0'; 
    n.queue=[];t=b.createElement(e);t.async=!0;
    t.src=v;s=b.getElementsByTagName(e)[0]; 
    s.parentNode.insertBefore(t,s)}(window, document,'script',  
    'https://connect.facebook.net/en_US/fbevents.js');
    fbq('init', '{your-pixel-id-goes-here}');
    fbq('track', 'PageView');
</script> 
<!-- End Facebook Pixel Code -->

The <noscript> tags must be removed since Cookiebot is a JavaScript solution, and noscript is for browsers that do not support JavaScript.
If you do include the <noscript> tag, then you may unintentionally be setting cookies without a visitor's consent.

Consent API

Meta has made a consent API available. You can use this API to prevent cookies from being set prior consent. Once cookie consent has granted, cookies can be used:

fbq('consent', 'revoke'); // Withdraws permission for cookies
fbq('consent', 'grant'); // Grants permission for cookies

To implement the API you'll need to set the permission using the fbq('consent', Cookiebot.consent.marketing ? 'grant' : 'revoke') method.
This checks if consent already has been given and sets the permission accordingly.

Here is how that looks:

!function(f,b,e,v,n,t,s) 
{if(f.fbq)return;n=f.fbq=function(){n.callMethod?
n.callMethod.apply(n,arguments):n.queue.push(arguments)};
if(!f._fbq)f._fbq=n;n.push=n;n.loaded=!0;n.version='2.0'; 
n.queue=[];t=b.createElement(e);t.async=!0;
t.src=v;s=b.getElementsByTagName(e)[0]; 
s.parentNode.insertBefore(t,s)}(window, document,'script',  
'https://connect.facebook.net/en_US/fbevents.js');
fbq('consent', Cookiebot.consent.marketing ? 'grant' : 'revoke');
fbq('init', '{your-pixel-id-goes-here}');
fbq('track', 'PageView');

To be able to react to changes in the consent settings, for example after the initial consent submission or a withdrawal a second script is needed:

<script>
window.addEventListener('CookiebotOnConsentReady', function (e) {
  fbq('consent', Cookiebot.consent.marketing ? 'grant' : 'revoke')
}, false)
</script>

More information: https://developers.facebook.com/docs/meta-pixel/implementation/gdpr