Overview
URL parameters, also known as “hidden fields”, can be used to customize your form with information you already know when you’re sharing it with respondents. For example:- Pre-filling fields with the email of the respondent
- Recording where your form was shared via a utm_source parameter (e.g., Facebook, Google, Instagram, etc.)
- Displaying the respondent’s name in the form to welcome them
How to add a URL parameter or hidden field
1
Open form settings
Click followed by 
URL parameters.2
Register a new parameter
+ Add new and enter a name for your parameter. In this example, we’ll choose “name”.
3
Reference the parameter in your form
You’re all set! We can now use it to:
- Pre-fill a field, by pressing referencing a value
- Write to any integration, by mapping this URL Parameter to some field like in Airtable or Notion
- Display in plaintext in the form by typing @ and choosing your parameter.
4
Share your form link
To make the URL parameter active in your form, you need to set its value in the form link. Here, we have a parameter called name registered, the default share link would look like: https://forms.fillout.com/t/9ofaEF4d54us?name=xxxxxSay we know that the respondent’s name that we’re sending our form to, Jane. We’ll type her name at the end of the link like this: https://forms.fillout.com/t/9ofaEF4d54us?name=jane
When you have multiple URL parameters for one form, you’ll need to separate them using an ampersand (&), like so: https://forms.fillout.com/t/your_form_id?email=jane@gmail.com&name=jane
Record URL parameters in submissions
You may want to track URL parameters in form submissions, like links shared on Facebook, Instagram, or LinkedIn to compare traffic. Fillout stores these by default on the Results page. If you’re using an integration, and want to write your URL parameters there as well, you can either: a. Create a Fillout field, set its Default value using a URL parameter, andHide always. If it’s linked to an integration, it will send the data without being shown to the respondent.
