Extend prefill for embed by mobile number (JavaScript)

  • 31 March 2024
  • 4 replies

Currently only name, email and custom questions can be prefilled using a call such as `Calendly.initPopupWidget`. 


However, in our use case the user's mobile number is also already known. Now the user has to re-enter his mobile number, reducing conversion and introducing extra work.

It would be helpful when the mobile number for text messages could be supplied programmatically too.

4 replies

Hey there @Guido08204 - thanks for your topic! 


Sorry you are running into issues with your embed. We have easy to follow articles in our Help Center that go over the Pre-Population of Invitee Information! 

Here is the first article you should check out. Please notice this callout in this Help Center article:

Select your website provider to learn more about the embed options available for your website.


If you're attempting to pre-populate the phone number for the SMS Text reminder field, unfortunately, this field cannot be pre-populated.


This is due to anti-spam laws and privacy regulations, that the “Send text messages to” field needs to be a separate field from any other phone number collection, cannot be a required field, and cannot be pre-filled.

I hope this helps! 

Thanks for the reply. However, it misses the point. The embed is already running well. I am aware it is not possible to fill out the SMS text field.

The topic is a suggestion to change the behaviour of Calendly.

As far as I know that are no reasons in GDPR (or “AVG” as it is called here in the Netherlands) why the containing site may not forward the data to Calendly.

The phone number has the same qualification as email address (it is not especially sensitive data). See

Forwarding the email address already assumes that there is a subprocessor agreement.

Hello again @Guido08204,


I will let our product team know about your request!


To share just a bit more information regarding this; the types of regulations we're contending with for SMS relevant to this policy are not exactly GDPR, but more so the governing bodies and carriers in charge of telecom infrastructure. Typically, SMS is a significantly higher-regulated field than email.


Thanks again,

Thank you for the background! I was not aware that there exist anti-spam laws for governing bodies and carriers of telecom infrastructure.