You can pass source codes from Action Network links on to an external URL using Thank You Page Redirects. This is especially helpful if you use ActBlue fundraising pages as your redirect, but it can work on any other site you want to redirect to as well. When someone takes action on your Action Network form, the source code they use is automatically passed through to the site people are being redirected. This can be used in conjunction with the URL-based redirects. This is useful in keeping source codes consistent across different platforms or services your organization may be using.
You can set this up in the 'Thank You Page Redirect' section of the 'Responses' tab on your Action Manage page. Insert the link you would like to redirect to. You can use any key in the argument (like refcode, if you're using ActBlue). More on keys and URL argument structure here. Then set the value as {{ source }}
For example:
If my action link is: https://actionnetwork.org/forms/myform?source=mysourceiscool
And I want to redirect people to: https://myurl.com?mytrackingkey={{ source }}
Then the redirect would be https://myurl.com?mytrackingkey=mysourceiscool
Note: This URL argument only works when sharing links over email, not via social media, your website, or anything else.