Microsoft hides file extensions in Windows by default even though it's a security risk that is commonly abused by phishing emails and malware distributors to trick people into opening malicious files.

FileTypesMan allows you to view, add, remove edit file extensions and types on Windows 11/10. You can always manually set or change File Associations & Extensions.

When it comes to converting file extensions on your iPhone, don't worry about downloading a third-party app when you can make the changes yourself.

You can create a file without a File Type Extension in Windows 11/10 by carefully following the steps laid down in this post.