> I can't imagine a real use case where you'd think this is desirable.

Not S3, but here's a literal real use case: the entry for the Iraqw word /ameeni (woman) in Wiktionary.

https://en.wiktionary.org/wiki//ameeni

If for whatever reason your S3 keys contained English words and their translations separated by a slash, you would have a real problem if one of your scripts were to concatenate woman, / and /ameeni as woman/ameeni instead of woman//ameeni in the English/Iraqw case.

Sounds like a Unicode problem. U+002F is not a letter codepoint and it's not appropriate to use as a letter given its history of being used for path separation. Iraqw slash should have its own code point.

Can they not just use a 3 like in Arabic?

If you’re working with a use case where that’s even possible, you need to URL-encode it like

  woman/%2Fameeni

Consider that if the language allowed trailing slashes. What would this path mean if ameeni/ happened to be a valid word?

  ameeni//ameeni

One of those would get the slash but it’s not clear which.

W3C says:

> The slash ("/", ASCII 2F hex) character is reserved for the delimiting of substrings whose relationship is hierarchical.

This exact issue has derailed our main document store for the past several years. We have written a couple supporting applications specifically to address the fallout from this issue.

If a user of S3 knows that directories aren't real why would they expect directory-related normalisation to happen?

Precisely because of it. On Linux, /bin/bash, //bin/bash and /bin//bash are the exact same file, the same inode. They look somewhat off to people, but they're entirely harmless, so cleaning that up is an aesthetic choice, not something important.

On S3 they're different. Using the wrong paths causes weird issues, like not finding things you expect you find, or storing multiple versions of the same data out of sync.

Normalizing // to / means making S3 behave more like people expect.

Another weird thing is that `foo/` is a valid object name in s3, so you can have both `foo/` and `foo` be different files.