When embedding a form on a WordPress page or post, the code retrieved from the Publish → Platforms → WordPress section within our form builder normally looks like this:
[ 123-contact-form i507842 ]
In order to prefill form fields you need to change this code in the following way (in one line):
[ 123-contact-form i507842 control3592242-1=John&control3592242-2=Doefirstname.lastname@example.org&control35 91577=This is a test message. ]
control3591576 are the name attributes of form fields. You can retrieve them by inspecting the code of your form with a browser inspection tool.
This is a test message. represent the prefilled values assigned to the fields above.
Name attributes and values are connected through the operator
Here is a list of the most frequently asked questions. For more FAQs, please browse through the FAQs page.
How does it work? I have been trying. How do I know what control id to use?
Here is a similar article which has a quick animation which shows how find the IDs of your fields: https://www.123formbuilder.com/docs/how-to-pass-user-input-from-one-form-to-another/