Booking form inside an embed can be prefilled as well.

Inline Embed

// Prefill Name, Email, Attendee Address and passing metadata - React.
// You can specify config property to do prefilling
// React Demo Link - https://codesandbox.io/s/react-prefill-attendee-address-email-sqhf7r
<Cal
  // .... other props in here
  config={{
    name: "Name",
    email: "[email protected]",
    // You will receive the value in payload.metadata["myKey"] in webhook.
    // Also, it would be stored in booking table under metadata column
    // It won't be shown on the booking details page.
    "metadata[myKey]": "myValue",
    location: JSON.stringify({
      value: "attendeeInPerson",
      // It can be any string that defines an address where the meeting would occur
      optionValue: "New York"
    })
  }}
></Cal>
// Prefill Name, Email, Attendee Address and passing metadata - Vanilla JS
// You can use 'inline' instruction to do the prefill
// VanillaJS Demo link - https://codesandbox.io/s/prefill-embed-fields-vanilla-js-zft44w?file=/index.html
Cal("inline", {
  config: {
    name: "Name",
    email: "[email protected]",
    // You will receive the value in payload.metadata["myKey"] in webhook.
    // Also, it would be stored in booking table under metadata column
    // It won't be shown on the booking details page.
    "metadata[myKey]": "myValue",
    location: JSON.stringify({
      value: "attendeeInPerson",
      // It can be any string that defines an address where the meeting would occur
      optionValue: "New York"
    })
  }
});
// Prefill Name, Email, Attendee Phonenumber and passing metadata - React
<Cal
  // .... other props in here
  config={{
    name: "Name",
    email: "[email protected]",
    // You will receive the value in payload.metadata["myKey"] in webhook.
    // Also, it would be stored in booking table under metadata column
    // It won't be shown on the booking details page.
    "metadata[myKey]": "myValue",
    location: JSON.stringify({
      value: "phone",
      // Any valid phonenumber in here
      optionValue: "+919999999999"
    })
  }}
></Cal>
// Prefill Name, Email and Attendee Phone - Vanilla JS
// You can use 'inline' instruction to do the prefill
Cal("inline", {
  config: {
    name: "Name",
    email: "[email protected]",
    location: JSON.stringify({
      value: "phone",
      // Any valid phonenumber in here
      optionValue: "+919999999999"
    })
  }
});

Floating button popup

// Prefill Name, Email, Attendee Phone and passing metadata - Vanilla JS
// You can use 'floatingButton' instruction to do the prefill
// This is common for React and VanillaJS embeds.
// Note that for React, Cal is not Cal component here it is Cal API.
Cal("floatingButton", {
  config: {
    name: "Name",
    email: "[email protected]",
    // You will receive the value in payload.metadata["myKey"] in webhook.
    // Also, it would be stored in booking table under metadata column
    // It won't be shown on the booking details page.
    "metadata[myKey]": "myValue",
    location: JSON.stringify({
      value: "phone",
      // Any valid phonenumber in here
      optionValue: "+919999999999"
    })
  }
});

Other location types and other fields can be prefilled in the similar way. You can find the correct value to give from here