Next step is to do custom first-party subdomain setup. It is recommended to set up the subdomain since receiving data through a first-party domain can help improve measurement performance.

Sub Domain setup:

• Provide a sub-domain name e.g., s2s or firstpartydata. Provide the domain name of the website on which tracking has to be setup. Once done, click ’Next’.
  

• A CNAME record will be generated which is required to be mapped in the domain manager to complete the sub domain setup.
  
  There is an option to email the instructions for setting up the sub-domain to the concerned team member e.g. IT team/domain manager. For ease of usage, the sub domain setup step by step instruction is also provided.
  Click this link to follow the DNS set-up steps for the respective Domain Manager platform you are using for your website.
• Click Proceed to move ahead. You can see the DNS propagation status for the record generated. It will move to the completed stage once the CNAME record has been added in the respective domain manager.
  
  
  
  You can see the Meta Conversions API Gateway setup overview with the selected details and the status along with the sub domain and domain setup.