Pre-filling
URL Parameters/Hidden fields
URL parameters are a powerful way to pass information to a Fillout form to support pre-filling and personalizing the form.
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
Register a new parameter
Go to Settings and click 
Enter a Parameter name. Here, we can tell Fillout to expect a URL Parameter with a certain name.Note that you can optionally provide a sample value for the parameter, if you’d like to see what your form looks like with that value being used (e.g. if you have some hide/show logic based on it).
URL parameters. Then, click + Add new2
Use the parameter in your form
You’re all set to start using your new URL parameter now! We can now use it to:
- Pre-fill a field, by pressing the
+icon on a Default value property of any field - Write to any integration, by heading to the Integrations at the top and creating a new connection or editing an existing one, and mapping this URL Parameter to some field like in Airtable or Notion.
- Display in plaintext in the form
3
Share your form link
To make the URL parameter active in your form, you need to set its value in the form link you share with respondents. For example, if we have a parameter called name registered, the default 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
Important: 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
Sample use cases
Personalize a form with URL parameters Type@ in any question or field to reference information from your form. Click the link icon on the left side of the pop-up followed by the parameter.
Publish your form and share it to your respondents.
Hide always through the right-hand settings panel. If this field is synced to an integration already, then it will automatically write to your integration without it ever being visible to the respondent:
