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Prefill fields link

Prefill fields links automatically fill out registration fields, perfect for registering people that are already on your mailing list.

Dewi avatar
Written by Dewi
Updated this week

The prefill fields link is an advanced method of registration that allows you to create registration page links that automatically fill out registration fields when opened.

Configuring the prefill fields link

The prefill fields link automatically includes all the registration fields that have been added to your webinar. By default, that’s only the first name and email address, but everything from company to phone number and even custom fields will be included in the link.

Follow the steps below to set up a prefill fields link:

  1. Find your webinar in your webinar overview and click its title

  2. Click ‘More’ on the right side below the registration page link

  3. Choose ‘Prefill fields link’

  4. Click ‘Link to webinar’

  5. Select the webinar and broadcast you want the prefill fields link to register recipients for

    An image of the 'Prefill fields link' interface

  6. Copy the link and paste it somewhere you can edit it

  7. Replace any text formatted as “First+name+here” with the information it asks for for configure your email software to replace this text automatically

  8. It’s now ready to be sent to your attendees!

Prefill fields link for webinar series

You can connect your prefill fields link to multiple webinars when you configure it for a webinar series. Simply click ‘Link to webinar’ once for each webinar in the series you want to automatically select when people use the prefill fields link.

An image of the 'Prefill fields link' interface in a webinar series

Please note! When you use the prefill fields link with a webinar series, take note that ‘Select webinars by default’ has priority over the broadcast selected when configuring the prefill fields link. This means that, even if you only select one of the webinars from the series during configuration, opening the link will still automatically select all of them on the registration page unless you disable ‘Select webinars by default’.

How do prefill fields links work?

By default, webinars only require a first name and email address for registration. That’s why prefill fields links only contain the first name and email address if your registration fields haven’t been edited. This is what they look like in that situation:

https://webinars.webinargeek.com/how-to-host-a-webinar?firstname=First+name+here&email=Email+here

The normal registration page link here is:

https://webinars.webinargeek.com/how-to-host-a-webinar

To prefill fields when someone opens the link, we add:

?firstname=First+name+here&email=Email+here

where “First+name+here” and “Email+here” are replaced by the recipient’s first name and email address.

So, for example, a prefill fields link with only the default registration fields could look like this:

https://webinars.webinargeek.com/how-to-host-a-webinar?firstname=Dewi&email=dewi@webinargeek.com

Each registration field you add to your webinar is added to the prefill fields link automatically. This means that it can get really long depending on the amount of registration fields you add. As an example, here is a prefill fields link for a webinar with ‘Surname’ and ‘Company name’ fields:

https://webinars.webinargeek.com/how-to-host-a-webinar?firstname=First+name+here&surname=Surname+here&email=Email+here&company=Company+name+here

As you can see, “&surname=Surname+here” and “&company=Company+name+here” were added because we added registration fields for a last name and company name.

Properly filled in, it could look like this:

https://webinars.webinargeek.com/how-to-host-a-webinar?firstname=Dewi&surname=from WebinarGeek&email=dewi@webinargeek.com&company=WebinarGeek

Every standard registration field works the same way.

Prefill fields links and custom registration fields

Prefill fields links also support custom registration fields, though they may be a little confusing to use. When you add a custom registration field, it’s added to the prefill fields link as “&extra_field_[numbers]=Label+here”, which means you can’t identify which field it is. However, “Label” is replaced with the label of your registration field.

So, if you create a custom field for, for example, a member number, you’d could get this:

&extra_field_12032=Member+number+here

As a whole, the link would look like this:

https://webinars.webinargeek.com/how-to-host-a-webinar?firstname=First+name+here&email=Email+here&extra_field_12032=Member+number+here

It works the same way as standard registration fields otherwise. Just keep in mind that the label is important for identifying which field it is in the prefill fields link!

Tips & tricks

Prefill fields link for follow-up emails

The prefill fields link is perfect for follow-up emails because you can use an attendee’s information from the previous webinar to sign them up for your new webinar. All you have to do is replace the text formatted as “First+name+here” with the correct email variables.

Below is an example of a prefill fields link modified for a follow-up email:

https://webinars.webinargeek.com/how-to-host-a-webinar?firstname={{first_name}}&email={{subscriber_email}}

In this example, {{first_name}} and {{subscriber_email}} will be automatically replaced by the recipient’s first name and email as they submitted them for the webinar the follow-up email comes from. This means that the information they entered for the previous webinar is automatically filled in on the registration page of the new webinar!

You can find a list of all our email variables in this article.

Sending prefill fields links from CRM software

Another situation where the prefill fields link feature is perfect is when you make use of CRM software, especially when integrated with WebinarGeek.

If you send the prefill fields link in an email from your CRM software, you can replace the text formatted like “First+name+here” with the software’s variables. This way, the software automatically replaces it with the email recipient’s data.

For example, if you’re using HubSpot, you could put the link in the email like this:

https://webinars.webinargeek.com/how-to-host-a-webinar?firstname={{contact.firstname}}&email={{contact.email}}

Because HubSpot automatically replaces {{contact.firstname}} and {{contact.email}} with the first name and email address of the email’s recipient.

What you have to replace the text formatted like “First+name+here” with depends on the CRM software you’re using, as each software works differently.

Advanced configuration

Prefill fields for embed forms

You can also configure embed forms to have prefilled fields for people that open them, though this requires more advanced configuration.

These instructions are for the embed forms that come with the new registration page that was introduced in June 2025. If you’re still using the previous version, please check this article for instructions instead.

The following values are available:

  • First name: firstname

  • Surname: surname

  • Email: email

  • Company name: company

  • Job title: job_title

  • Country: country

  • Street: street

  • House number: house_number

  • Zipcode: postcode

  • City: city

  • State / Province: province

  • Phone number: phone

  • Discount code: webinar_discount_code

  • Extra fields: extra_field_[id]

First, you need to add the “initialFormState” property to your embed code alongside the fields you’re looking to prefill. You can find an example below:

<div id="mw_2flmt1TRxRO_webinargeek"></div>
<script>
(function(w,d,stn,sa,gn,se,fse){w[gn]=w[gn]||function(){(w[gn].q = w[gn].q||[]).push(arguments)};
se=d.createElement(stn);fse=d.getElementsByTagName(stn)[0];se.id=gn;se.async=1;
se.src=sa+'?t='+new Date().toISOString().slice(0, -9);fse.parentNode.insertBefore(se, fse);
})(window, document, 'script', 'https://malong.webinargeek.com/malong.embed.js', 'mw_2flmt1TRxRO');
mw_2flmt1TRxRO("init", {
project: "registration",
identifier: "2c257112-3c36-4ed2-908a-3fbad1b46d22",
shape: "inline",
// Add the initialFormState property, fill it programmatically
initialFormState: {
firstname: "First name here",
surname: "Surname here",
email: "Email here",
company: "Company name here",
job_title: "Job title here",
country: "NL",
street: "Street here",
house_number: "House number here",
postcode: "Zipcode here",
city: "City here",
province: "State / Province here",
phone: "Phone here",
webinar_discount_code: "Discount code here",
extra_field_[id]: "Text field 1 here",
extra_field_[id]: "Option 1",
"episode4502": 29497,

}
});
</script>

Afterwards, you have to programmatically fill in the data for the values. You can find the ID of your custom registration fields in the prefill fields link interface.

Troubleshooting

I see the wrong information in the registration fields when I open my prefill registration link.

When you open a WebinarGeek registration page, fill in your information and then close the page, we save the information you entered. This is so that, if webinar registrants accidentally close the page mid-registration, they don’t lose their progress. However, this saved information overrides the prefill fields link, which means that if you ever opened the registration page before using the prefill fields link and entered information, you’ll see that information instead of what you’ve added to the prefill fields link.

If this is happening to you, you can open the prefill fields link in an incognito window instead. Incognito browser windows reset their saved information each time they’re closed and reopened.

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