# Boldface arrows in tikzcd

I want to make some of the arrows in my tikzcd diagram bold, but not all of them. How? Say, just the horizontal arrows in the following MWE:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{tikz-cd}

\begin{document}

$\begin{tikzcd}[column sep=small, row sep=small] \ddots \arrow[rd] & & & & M_2 \arrow[rd, hook] & & & & & \\ \cdots \arrow[r] & F_3 \arrow[rr, "d_3"] \arrow[rd, two heads] & & F_2 \arrow[rr, "d_2"] \arrow[ru, two heads] & & F_1 \arrow[rd, two heads] \arrow[rr, "d_1"] & & F_0 \arrow[r, "\varepsilon"] & M \arrow[r] & 0 \\ & & M_3 \arrow[ru, hook] & & & & M_1 \arrow[ru, hook] & & & \end{tikzcd}$

\end{document}

• just add option thick. for example \cdots \arrow[r,thick] & F_3 \arrow[rr,thick, "d_3"] ... tikz-cd is based on tikz that meaning, you can use options from it. – Zarko Feb 17 '19 at 21:32
• @Zarko Thank you, this is almost what I wanted. Do you know if is there any way of not increasing the size of the arrowheads together with the thickness of the arrow? – Ivo Terek Feb 17 '19 at 21:35
• see ctan.math.washington.edu/tex-archive/graphics/pgf/contrib/… and my answer below. – Zarko Feb 17 '19 at 21:54

tikz-cd is based on the package tikz. theas enable to define styles of tikzcd images elements similarly as at pure tikz pictures. specific how to change forms of tikzcd images see tikz-cd documentation.
\documentclass[varwidth,margin=3mm]{standalone}
$\tikzset{LA/.style = {draw=red, % just to demonstrate, where LA is used line width=#1, -{Straight Barb[length=3pt]}}, LA/.default=1pt } \begin{tikzcd}[column sep=small, row sep=small] \ddots \arrow[rd] & & & & M_2 \arrow[rd, hook] & & & & & \\ \cdots \arrow[r,LA] & F_3 \arrow[rr,LA=0.5pt, "d_3"] \arrow[rd, two heads] & & F_2 \arrow[rr, "d_2"] \arrow[ru, two heads] & & F_1 \arrow[rd, two heads] \arrow[rr, "d_1"] & & F_0 \arrow[r, "\varepsilon"] & M \arrow[r] & 0 \\ & & M_3 \arrow[ru, hook] & & & & M_1 \arrow[ru, hook] & & & \end{tikzcd}$