# Why does xelatex produce a different binary of the pdf each time? [duplicate]

This is doc.tex

\documentclass{article}
\begin{document}
a
\end{document}


Then I xelatex doc.tex and md5 doc.pdf, so I get a unique md5 code. If I run xelatex again on the same tex file it produces a diff pdf (diff md5).

What can I do for xelatex to procude the same md5 result for the same tex file?