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Pre-fill information you already know about a client, or hide fields meant only for internal tracking (like referral sources or Lead IDs), to keep your Cal ID booking form short and friction-free while your calendar stays organized.

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Step 1: Add a booking question

1

Log in to Cal ID

Log in to your Cal ID account.
2

Select your event

Go to Event Types and open the event you want to change.
3

Open the Advanced tab

Click the Advanced tab in the top navigation bar.
4

Add a question

In the Booking questions section, click + Add a question.
Booking questions section of the Advanced tab listing the default name and email questions with the + Add a question button beneath them

Where your intake fields live

5

Fill out the question details

  • Label: The question text (e.g., “Referral Source”).
  • Identifier: Take note of this unique ID (e.g., referral). You’ll need this exact word to pre-fill the data later.
Add a question dialog with the Input type dropdown, the Label field, the Identifier field and a Placeholder field filled in

Noting the identifier you will prefill

6

Add the question

Click Add.

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Step 2: Hide a booking question

To record a field in your calendar while keeping it invisible to the booker, hide it:
1

Locate your question

Find your newly added question in the list.
2

Set it to Hidden

Click the switch next to the question to set it to Hidden.
3

Lock the value (optional)

To ensure a booker cannot change a pre-filled value even if they find the field, click Edit and check the box “Disable input if the URL identifier is prefilled”.
4

Save

Click Save at the top right of the page.

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Step 3: Pre-fill the booking question

To automatically fill a field, append a query parameter to your booking link that matches your question’s Identifier.
  • The logic: Use a ? for the first parameter and an & for any additional parameters.
  • The structure: URL?identifier=value
Booking link with ?referral=Instagram appended, shown above a booking form where the Referral Source field is already filled in

Passing a value in the link

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Example scenario

  • Your booking link: https://cal.id/username/eventtype
  • Your identifier: referral
  • The value you want to set: Instagram
Your modified URL becomes: https://cal.id/username/eventtype?referral=Instagram

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Example with multiple parameters

If your URL already has parameters (like ?overlayCalendar=true), use the & symbol to add your pre-fill data: https://cal.id/username/eventtype?overlayCalendar=true&referral=Instagram

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URL parameter behavior

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Why use this method?

  • Data integrity: As long as the question is Hidden, the booker won’t see it on the page, but the information (e.g., “Referral: Instagram”) still appears in your Google/Outlook Calendar and your Cal ID Dashboard once scheduled.
  • Personalized links: Send custom links to different partners, each with their own name pre-filled, to see exactly who is driving your bookings.
  • Clean forms: Keep the visible form short by capturing background data (like Campaign IDs or User IDs) behind the scenes.

Add pre-booking questions

Explore every input type and build your intake form.

Require or exclude email domains

Control who can book with domain validation rules.

Related topics

Add Pre-Booking Questions for EventsSplit Full Name into First and Last Name on Booking PageDisable Adding GuestsRequire or Exclude Email Domains