Colon in bibtextkey

Question

I always use colons when denoting items in my bibliography (in a .bib file): Lee:05, Smith:11, etc.

However, Jabref says that

Some characters should not be used in bibtexkey as they are not compatible or not recommended: { } ( ) , \ " - # ~ ^ : ' (note the colon!)

What's the problem with the colon? Should I expect to have some issues with my bibliography because of that?

See also: What characters are allowed to use as delimiters for BibTeX keys? — leandriis, Jul 30 '20 at 17:23
The answer to this question does not report any problems with the colon. Does it mean it's safe to use it? — Dmitry, Jul 30 '20 at 17:29
Depending on the laguage you use, the colon could cause problems. See also: https://tex.stackexchange.com/q/89016/134144 — leandriis, Jul 30 '20 at 18:04
@leandriis, that's an important point, thank you! I mostly use it with English and Russian. So far there were no problems, but if any problem appears, I will know what can be the potential reason for that. — Dmitry, Jul 30 '20 at 18:10

moewe · Accepted Answer · 2020-07-31T12:26:20.753

There are two aspects to asking whether a character is safe in entry keys.

The character needs to be safe when it is read by BibTeX (or Biber) in the .bib file.
The character needs to be safe when it is later processed by LaTeX.

Examples of characters that are unsafe on the .bib side would be ,, =, { and }. Those characters have special meaning in the .bib file syntax and cannot be used in entry keys as that would confuse BibTeX or Biber when they parse the .bib file.

One example of an unsafe character on the LaTeX side is ~. ~ is absolutely fine on the .bib file side, but it has a special definition for LaTeX (inserting a non-breakable space). The following MWE therefore breaks

\documentclass{article}
\usepackage{natbib}
\begin{filecontents}{\jobname.bib}
@book{appleby~1980,
  author  = {Humphrey Appleby},
  title   = {On the Importance of the Civil Service},
  year    = {1980},
}
\end{filecontents}
\begin{document}
\cite{appleby~1980}
\bibliographystyle{plainnat}
\bibliography{\jobname}
\end{document}

(Note that biblatex can accept entry keys with ~.)

The : is not problematic on the .bib side of things, since : does not have a special meaning in the .bib file syntax.

Depending on your language settings, : either behaves as normal or has a special definition (e.g. in French). If the colon has a special definition, it is potentially dangerous. But all bibliography and citation setups that I tested (of course I only tested the usual ones) take precautions against problems with :, so the following MWE compiles fine.

\documentclass[french]{article}
\usepackage[T1]{fontenc}
\usepackage{natbib}
\usepackage{babel}
\begin{filecontents}{\jobname.bib}
@book{appleby:1980,
  author  = {Humphrey Appleby},
  title   = {On the Importance of the Civil Service},
  year    = {1980},
}
\end{filecontents}
\begin{document}
\cite{appleby:1980}
\bibliographystyle{plainnat}
\bibliography{\jobname}
\end{document}

A similar example also works fine with biblatex. Indeed, the biblatex examples file biblatex-examples.bib makes ample use of colons in entry keys.

However, the occasional problem with colons pops up from time to time, see leandriis' link Colon in bibliography keys incompatible with babel, biblatex and tex4ht.

This is an ultimate answer. Thank you! – Dmitry Jul 31 '20 at 08:32 — Dmitry, Jul 31 '20 at 08:32

Colon in bibtextkey

1 Answers1