By default, anyone can subscribe to your calendar without giving you any details. If you want to know who your subscribers are, you can require them to provide their information first. This is a premium feature.
This article covers the calendar-side settings that gate subscription behind a form. Building the form itself (adding custom fields) is covered separately in Custom RSVP forms.
Choose how people subscribe
Open your calendar's settings (create or edit a calendar) and find the Subscriber Information Collection section. You have two options:
Allow anonymous subscriptions (no data collection): the default. People can subscribe without giving you any details.
Collect subscriber information before subscription: people must complete a form before they can subscribe.
Select Collect subscriber information before subscription to turn collection on. Two more options appear below it.
Hide event details until information is provided
When you turn on collection, you can tick Hide event details until information is provided. With this enabled, visitors see only the form when they open your calendar: the event list stays hidden until they submit their details.
Leave it unticked if you want people to browse the events first and provide their information only when they go to subscribe.
Choose what to collect
Use the Custom Form dropdown to decide which fields the form asks for:
No custom form (basic name and email only): the default. The form collects a name and an email address.
A custom form you have built: collects whatever fields that form contains.
To collect more than a name and email (for example a company, a phone number, or a country), build a custom form first and then select it here. See Custom RSVP forms for how to create one.
What subscribers see
The experience on your public calendar page depends on your settings:
Anonymous subscriptions: visitors see your events and the subscribe buttons straight away.
Collection on: a form appears above the event list. Visitors fill it in and click Register to follow calendar, then the subscribe buttons appear.
Collection on with details hidden: visitors see only the form until they submit it, then the events and subscribe buttons appear.
Where the information goes
Everything you collect is attached to each subscriber. You can view and manage it from your calendar's subscriber list. See Manage calendar subscribers.