Stripe checkout - Remove or make email field read only

A possible work around:

You can use customer_email instead customer parameter when you create a session. In this case users can not change the value of email field.

Then, you can get the created customer and update it if you need added some data using the API: https://stripe.com/docs/api/customers/update

But, the problem is that stripe will create a new customer for each checkout.

I got an email from stripe today

We are disabling customers’ ability to overwrite their email address
Starting October 26, customers can no longer edit their email address after you pass it into a Checkout Session. We’ve made this change to prevent duplicative subscriptions from being created by accident for existing customers and prevent unexpected updates to the Customer object during Checkout.

And here it is in all its glory

Now, according to the Docs:

If the customer changes their email on the Checkout page, the Customer object will be updated with the new email.

Given that Stripe allows "customers" to change the email id. we pass to the Checkout form, an idea that could work for you is to add your "internal" identifier (be it an email or other internal user id) as Metatadata to the customer you create, like so (below code is in c#, but you get the idea):

Dictionary<string, string> customerMetaData = new Dictionary<string, string>();
customerMetaData.Add("myappuserid", "{useyourinternalidhere}");

var customer = await cs.CreateAsync(new CustomerCreateOptions { Email = "{emailthat youwanttouseforcustomer}", Metadata = customerMetaData });

//Now you can pass this customer when you create the session for checkout

The point being whatever email the user ends up using, you can always get the corresponding internal user id as well from the customer object's metadata.

In the "success" call back, you can then retrieve the customer data and then save the returned customer details - including the stripe customer id / email that end user used in check out form / your own internal id that you can now retrieve from the customer metadata -- that way you can maintain a mapping of stripe's details to your own internal customer details.

//This code is on the "success" call back (when the session id. is passed)
var sessionService = new SessionService();
var session = await sessionService.GetAsync(session_id, new SessionGetOptions { Expand = new List<string> { "customer" , "line_items", "subscription" } });
var sessionCustomer = session.Customer;

//This sessionCustomer now has the metadata that you passed while creating the customer
//Save the Stripe ids / email id along with data retrieved from the Metadata;
//Now you have all the info you required..

Of course this response is delayed - hopefully, it helps others...

Use "customer_email" parameter as shown below and this is the example in Python:

checkout_session = stripe.checkout.Session.create(
    customer_email='example@gmail.com', # Here
    line_items=[
        {
            'price_data': {
                'currency': 'jpy',
                'unit_amount': 1000,
                'product_data': {
                    'name': 'Honey',
                    'description': 'Good honey',
                },
            },
            'quantity': 1,
        },
    ],
    mode='payment',
    success_url= "https://example.com/success.html",
    cancel_url='https://example.com/cancel',
)

And because you use "customer_email" parameter so the email field is readonly as shown below: