What are URL parameters?
URL parameters are information added to the end of a link. They start with a question mark? and use key-value pairs in the format key=value. Multiple parameters are separated by an ampersand &.
For example: https://forms.fillout.com/t/9ofaEF4d54us?name=Jane+Doe
Here, name=Jane Doe is the URL parameter.
Video tutorial
How URL parameters work
With URL parameters, you can pass information to a Fillout form, such as a respondent’s name, email, or where they came from. This information is stored in hidden fields. You can use it to:- Pre-fill fields with information you already know, like a respondent’s email
- Display information in the form, such as a respondent’s name
- Track where your form was shared via a utm_source parameter (e.g., Facebook, Google, Instagram, etc.)
- Write data to any integration with mappings
How to add a URL parameter or hidden field
1
Open form settings
Click the 
gear icon on the top right.2
Register a new parameter
Click 
URL parameters followed by + Add new, then enter the parameter. In this example, we’ll choose “name”.3
Reference the parameter in your form
There are many ways you can use URL parameters as listed above. In this example, we’ll show a respondent’s 
name at the beginning of the form.Type @ and click the link icon , then choose your parameter.Hide always.4
Share your form link
To activate a URL parameter, add its value to the form link. For example, if you have a name parameter, add the respondent’s name at the end of the link: https://forms.fillout.com/t/9ofaEF4d54us?name=jane
+- use a plus icon to space out values (e.g. Jane+Doe)&- use an ampersand to separate different types of parameters (e.g email=jane@gmail.com&name=Jane+Doe)
Send URL parameters to integrations
Fillout stores URL parameters by default on the Results page. Aside from the name and email, this can be language used, links shared on Facebook, Instagram, or LinkedIn to compare traffic, and many more.
link icon in the picker.
In some cases, the URL parameter may not show up in the picker. A workaround is to create a hidden field and map that instead. See step 4 below.
Track the form language used in responses
1
Register your URL parameter
If you haven’t already, create one first following the steps above. In this example, we’ll record the language used. Label the parameter as
lang.Enabling language translations is available on the Starter plan and above. More info here.
2
Enable translations
In your form settings, add the languages you’d like the form to be available in.
By default, respondents will see a language picker. This can be hidden using CSS if needed. More info here.
3
Map it to your integration
If you haven’t connected an integration yet, click
Integrate on top to connect.Under Mappings, link your URL parameter, which can be found by clicking the link icon .4
Create a hidden field (if needed)
In cases where the URL parameter can’t be directly mapped, follow step 3 of this section to prefill a hidden field with the 
langparameter, then map this field to your integration.5
Publish and share your form link
By default, respondents can choose their language from a language picker. Their selection is recorded as its language code (e.g., French → fr). (See the list of language codes below.)
Send data between forms
You can pass data from a main form to a subform using URL parameters so respondents won’t need to re-enter the same information. Check out this guide.Other advanced features
Form parameters
Share data between forms with URL parameters.
Pre-fill fields
Pre-populate fields based on previous inputs and more.
Answer piping
Insert previous answers into upcoming questions or fields.