> ## Documentation Index
> Fetch the complete documentation index at: https://cal.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Registration window

> Choose when guests can start and stop registering for a Cal Event, and see what guests are shown on the event page and embed before, during and after the window.

By default, guests can register for a Cal Event from the moment you publish it until the event
starts. Set a registration window to open registration later, for example at a set launch time, or to
close it before the event starts so you can lock the guest list.

![The Settings tab under Attendance in the Cal Event editor, with the Registration window section showing a Registration opens time and a Registration closes time](https://mintcdn.com/calcom/DiOTolP2mA750GqH/images/cal-events-registration-window/editor-registration-window.png?fit=max\&auto=format\&n=DiOTolP2mA750GqH\&q=85\&s=c5a78d6e66b570f4081c27b3dd5f30d1)

## Set the registration window

**1. Open the event's settings**

Go to **Events**, open the event, and select **Attendance** → **Settings**.

**2. Choose when registration opens**

Under **Registration window**, pick a date and time for **Registration opens**. Leave it empty
(it reads **When published**) to open registration as soon as the event is published.

**3. Choose when registration closes**

Pick a date and time for **Registration closes**. Leave it empty (it reads **When the event
starts**) to keep registration open until the event starts.

**4. Save**

Save the event. The preview next to the editor shows what guests see right now.

Times are set in the event's time zone, and the pickers don't offer anything after the event starts.
To go back to the default for either time, clear it with the clear button next to the picker.

### Rules for the window

Cal.com checks the window when you save:

| Rule | Message if it's broken |
| - | - |
| Registration must close at or before the event starts. | **Registration must close at or before the event start** |
| Registration must open before it closes. If you didn't set a close time, it must open before the event starts. | **Registration must open before it closes** |

The message appears under the picker that needs changing. If you save from another tab, the editor
opens **Attendance** → **Settings** so you can fix it. The same rules apply when you move the event's
start time: a new start time earlier than the registration close time can't be saved.

If you change the event's time zone, the registration times keep the same date and time on the clock
in the new time zone.

### Who can change the window

These people can set and clear the registration window:

* The event's hosts
* Team members whose role lets them edit the team's events
* The owner of a personal event

Co-hosts see both pickers turned off with **Contact the main host to change this setting**. They can
still save their other changes to the event, and their saves leave the window as it is.

> [!NOTE]
>
> Duplicating an event doesn't copy its registration window. Set it again on the new event.

## What guests see

The event page, the embed and the editor preview show guests where the event is in its registration
window. The page updates when registration opens or closes, without a reload.

![A Cal Event's public page where the Registration panel shows Registration not open yet and the date and time registration opens](https://mintcdn.com/calcom/DiOTolP2mA750GqH/images/cal-events-registration-window/public-page-not-open-yet.png?fit=max\&auto=format\&n=DiOTolP2mA750GqH\&q=85\&s=d1af3f9e3afeba7d95d87dbf07b49988)

| When | Event page | Embed |
| - | - | - |
| Before registration opens | **Registration not open yet**, with **Registration opens** and the date and time underneath, and a **Notify me** button. Guests can't register yet. The **Register with iMessage**, **Register by text message** or **Register with WhatsApp** button is hidden. | **Registration not open yet** and **Notify me** |
| While registration is open | The usual **Register**, **Request to join** or **Join waitlist** button. If you set a close time, **Registration closes** and the date and time are shown underneath. | Registration as usual |
| After a close time you set | **Registration closed**, with **Registration for this event has closed**. | **Registration for this event has closed** |
| After the event starts, with no close time set | **Registration closed**, with **This event has already started**. | **Registration for this event has closed** |

Dates and times on the event page are shown in the guest's time zone, with the time zone's short
name.

![A Cal Event's public page with the Join waitlist button and the date and time registration closes shown underneath](https://mintcdn.com/calcom/DiOTolP2mA750GqH/images/cal-events-registration-window/public-page-closes-at.png?fit=max\&auto=format\&n=DiOTolP2mA750GqH\&q=85\&s=cc75e4b07c64b9acb76f61f918cd1e8e)

Guests who are already registered, on the waitlist or waiting for approval keep seeing their own
registration status instead of the window. A cancelled or ended event shows that state instead.

### Notify me

Before registration opens, guests can select **Notify me** on the event page or the embed and leave
their email. Signed-in guests subscribe their account's email in one tap. Cal.com sends each of them
one email when registration opens, with a link to the event page.

If you move the open time later, or clear it, the email follows the new time. Guests aren't emailed
if you cancel the event or registration closes before they're told. Every email has an unsubscribe
link, and the list of addresses is deleted once the event ends.

### How the window is enforced

Cal.com checks the window on its own clock every time someone registers, so a guest can't register
outside the window from an old tab or by texting an RSVP. Joining the waitlist counts as
registering and follows the same window.

Promoting guests who are already on the waitlist doesn't. If a seat frees up after registration
closes, guests on the waitlist can still be promoted into it, by a host or automatically, until the
event starts.

## Set the window with the API

You can also set the window with `registrationOpensAt` and `registrationClosesAt` when you
[create an Event](https://cal.com/docs/api-reference/v2/events/create-an-event.md) or
[update an Event](https://cal.com/docs/api-reference/v2/events/update-an-event.md) with API v2. Send times in ISO 8601 in
UTC, or `null` to use the default. The same rules apply as in the editor.

## Set the window with the assistant

You can also ask the [Cal.com assistant](https://cal.com/docs/agents.md#change-a-cal-events-registration-window-through-the-assistant) when registration opens and closes, or to set or clear either time. It shows the new window on an approval card before saving, and the same rules apply as in the editor.


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