Why Blob Resource is downloading?

I inspected my unity webgl build in chrome and found two blob files (downloaded)

request url : blob:http://localhost/83fb9348-ae51-4802-9dbb-373ab074c8e3

request url : blob:http://localhost/0d4181cb-4229-469d-89eb-d1761ad8a9b4

what is this? can i restrict it? cause it will require content security policy header