Case sensitivity in HTTP
According to HTML and URLs
URLs in general are case-sensitive (with the exception of machine names). There may be URLs, or parts of URLs, where case doesn’t matter, but identifying these may not be easy. Users should always consider that URLs are case-sensitive.
According to RFC 7230
Each header field consists of a case-insensitive field name followed by a colon (“:”), optional leading whitespace, the field value, and optional trailing whitespace.
URLSession, mostly we will get
request.httpMethod = "GET" and
request.httpMethod = "get". Generally speaking, you should use some popular wrappers Alamofire or Malibu as they are mature enough. Spend your precious time solving more important problems instead.
According to RFC 7231
The method token is case-sensitive because it might be used as a gateway to object-based systems with case-sensitive method names.