Hello @anil kumar ,
Thank you for reaching out to the Microsoft Q&A platform. Happy to answer your question.
Most of this resource naming restrictions for case/char sensitive in azure resource naming convention are for the fact that each resource in the backend as a string created for it.
Example - Storage account, if we check the properties, we have a URI and a Host name cannot support space OR capital letters as per the RFC's. Otherwise it will result in URL Character Encoding Issues.
Reference : RFC 1738 - Uniform Resource Locators (URL) (RFC1738) (faqs.org)
Regarding the Capital letters, it is only for storage accounts and some resources. VMs, NIC interfaces and Disks etc., have capital letters in them.
This article summarizes naming rules and restrictions for Azure resources. For recommendations about how to name resources, see Naming rules and restrictions for Azure resources
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