Some Chinese characters can no show using ctex

Question

I use overleaf to edit my CV, but I find a character "珅" in Chinese cannot be shown in the compiled PDF. I also try XeCJK, but it doesn't work too. Here is my code:

\documentclass[a4paper]{article}
\usepackage[UTF8]{ctex}
\begin{document}
珅
\end{document}

Answer 1

The default fontset (fandol) loaded by ctex and xeCJK may not have glyphs for many archaic Chinese characters. If you're compiling this on Overleaf, you can use the fontset=ubuntu option to load Noto Serif CJK SC:

\usepackage[UTF8,fontset=ubuntu]{ctex}

Or if you prefer to load the font explicitly:

\usepackage{ctex}
\setCJKmainfont{Noto Serif CJK SC} % or some other font that has the glyph

Answer 2

I’m going to expand on imnothere’s fine answer with a few best practices.

\documentclass[a4paper]{article}
\tracinglostchars=2
\usepackage[UTF8, fontset=none]{ctex}

\defaultfontfeatures{ Scale=MatchUppercase,
                      Ligatures=TeX,
                      Renderer=HarfBuzz }

%% Noto CJK fonts available at
%%  https://www.google.com/get/noto/help/cjk/
\setmainfont{Latin Modern Roman}[Scale=1.0]
\setCJKmainfont{Noto Serif CJK SC}
\setCJKsansfont{Noto Sans CJK SC}
\setCJKmonofont{Noto Sans Mono CJK SC}

\begin{document}
珅
\end{document}

• You want \tracinglostchars=2 so that TeX will give you a warning when your font is missing a character. Without this command, the warning will be silently buried in the middle of your .log file.
• In LuaLaTeX as of 2020, you need to load your CJK fonts with the Renderer=HarfBuzz, or you will get an out-of-memory error. XeTeX uses HarfBuzz by default and works fine. XeLaTeX should give you a benign warning if it sees Renderer=.
• You probably want a Scale= option if you are mixing different fonts.
• You might wish to set sans-serif and monospace fonts as well.
• If you would be overloading the font set from the package anyway, you can skip loading one with fontset=none.