Are URIs case-insensitive?

http protocols specifications rfc2616
user1968030 picture user1968030 · Mar 26, 2013 · Viewed 20.5k times · Source

When comparing two URIs to decide if they match or not, a client
SHOULD use a case-sensitive octet-by-octet comparison of the entire
URIs, with these exceptions:

I read above Sentence in Http Rfc I think Url is case-insensitive but i dont undrestand what that means ?

Answer

Remy Lebeau picture Remy Lebeau · Oct 4, 2014

RFC 3986 states:

the scheme and host are case-insensitive and therefore should be normalized to lowercase. For example, the URI <HTTP://www.EXAMPLE.com/> is equivalent to <http://www.example.com/>. The other generic syntax components are assumed to be case-sensitive unless specifically defined otherwise by the scheme

RFC 2616 defines the following comparison rule for the HTTP scheme:

When comparing two URIs to decide if they match or not, a client SHOULD use a case-sensitive octet-by-octet comparison of the entire URIs, with these exceptions:

However, RFC 7230 locks it down further by stating:

The scheme and host are case-insensitive and normally provided in lowercase; all other components are compared in a case-sensitive manner.

Those rules typically apply to client side comparisons. There are no rules specifically geared for server side comparisons. Once a server breaks up a URI into its components, it should treat them according to the same rules, but I don't see that enforced in the RFCs. Some web servers, like Apache, do follow the rules. IIS doesn't, for compatibility with Windows' case-insensitive file system.

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