# Is biblatex sorting option sortcase sorting sensitively or case insensitively by default?

This is what the biblatex documentation says on the sortcase option:

I am not a native English speaker. Therefore, after reading that, I am not really sure whether sortcase=true means it will eventually sort case sensitively or case insensitively.

In

[sortcase] Whether or not to sort the bibliography and the list of shorthands case-sensitively.

sortcase=true means that sorting is case sensitive. sortcase=false means sorting is case insensitive. This may become slightly clearer from the Biber documentation, which has

Collation is by default case sensitive. You can turn this off globally using the Biber option --sortcase=false or from Biblatex using its option sortcase=false. [...] By default, Biber collates uppercase before lower. You can reverse this globally for all sorting using the Biber option --sortupper=false or from Biblatex by using its option sortupper=false.

You can experiment with that in

\documentclass[british]{article}
\usepackage{babel}
\usepackage{csquotes}

\usepackage[style=authortitle, sortcase=true, sortupper=true, backend=biber]{biblatex}

\begin{filecontents}{\jobname.bib}
@book{appleby:ua,
author  = {Humphrey Appleby},
title   = {A},
date    = {1982},
}
@book{appleby:la,
author  = {Humphrey Appleby},
title   = {a},
date    = {1985},
}
@book{appleby:ub,
author  = {Humphrey Appleby},
title   = {B},
date    = {1984},
}
@book{appleby:lb,
author  = {Humphrey Appleby},
title   = {b},
date    = {1983},
}
@book{bppleby:ua,
author  = {Humphrey Bppleby},
title   = {AK},
date    = {1982},
}
@book{bppleby:la,
author  = {Humphrey Bppleby},
title   = {al},
date    = {1985},
}
@book{bppleby:ub,
author  = {Humphrey Bppleby},
title   = {BL},
date    = {1984},
}
@book{bppleby:lb,
author  = {Humphrey Bppleby},
title   = {bk},
date    = {1983},
}
\end{filecontents}

\nocite{*}
\begin{document}
\printbibliography
\end{document}


## sortcase=false

This example also shows that case sensitive sorting only becomes important if there is a tie when we only look at the letters.

• "ak"/"AK" always sorts before "al"/"AL", no matter what capitalisation the two letters use.

• But "A" only sorts before "a" with sortcase=true (and sortupper=true).

If I understand correctly this behaviour is consistent with the Unicode Collation Algorithm: https://unicode.org/reports/tr10/.