Nils Toedtmann asked:
Is it safe to use http(s)://CompanyName.com/xyz as URL (e.g. for branding purposes) without any changes to the service-side configs?
I know that DNS is case-insensitive, but could there still be side-effects? I am thinking of e.g. various parts of the chain failing to match CompanyName.com ~ companyname.com:
- Some web backend might fail to match
- Some load balancer/proxy/cache/application layer firewall might fail to match
- Some client might apply same-origin policies wrongly
- Some client might fail to match in certificate checks
- While DNS is generally case-insensitive, could IDNs change the picture?
Anyone experienced those or other issues with capitals in the hostname part of URLs?
@Michael Hampton pointed out that, according the the HTTP standards, the hostname IS case-insensitive, but some software is non-compliant in this regard.
I try to get a sense of how prevalent non-compliant software is, in particular clients. I assume all recent major browsers are fine, but what e.g. about mobile apps? (Should I better split this off into a separate SF question?)
Yes, the hostname really is case-insensitive, as specified in RFC 3986 § 3.2.2, because hostnames in general are case-insensitive in the DNS. This RFC also gives recommendations on how to avoid the problems you mentioned:
Although host is case-insensitive, producers and normalizers should use lowercase for registered names and hexadecimal addresses for the sake of uniformity, while only using uppercase letters for percent-encodings.
I have seen at least one HTTP cache (W3 Total Cache) which does not normalize the hostname in this manner, and ends up caching content multiple times, e.g. under
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