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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

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How to add a URL parameter or hidden field

1

Register a new parameter

Go to Settings and click URL parameters. Then, click + Add new
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).
2

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

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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.
Recording 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 and pre-fill it with a URL parameter under Default value. Then, set it to 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:
b. Head to your integration settings, and map the URL parameter directly. E.g. for Airtable, there is a Mappings section which you can use for this purpose. See this article for more information.

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Other advanced features

Pre-fill fields

Pre-populate form fields based on previous inputs, URL parameters, and more.

Answer piping

Insert respondents’ prior input into fields for a personalized experience.