How do you write a checkmark(✓) in LaTeX?

Although the checkmark symbol is the same, there is more than one slight morphological difference that can be noticed in different documents or books.

And every difference is pointed out in latex for which there are separate commands and packages.

Package	Command and Output
amsmath	\checkmark →
MnSymbol	Same as  →
fdsymbol	Same as →
boisik	Same as →
bbding	\Checkmark →
pifont	\ding{51} →
arev	\ballotcheck →
utfsym	\usym{1F5F8} →

\documentclass{article}
\usepackage{MnSymbol,utfsym,arev}
\begin{document}
   \[ \checkmark \]
   \[ \usym{1F5F8} \]
   \[ \ballotcheck \]
\end{document}

Output :

Use of nine different packages is shown above. You can use whatever you think is your best practice.

Heavy checkmark symbol in LaTeX

As you can see, the font style of the symbol will be bold in case of heavy checkmark.

For this, the symbols are represented below with the help of some important packages.

\documentclass{article}
\usepackage{stix,bbding,pifont,utfsym,fontawesome}
\begin{document}
   % Math mode commands   
   $ \checkmark $\\[6pt]
   $ \usym{2713}, \usym{2714} $\\[6pt]
   % Text mode commands
    \CheckmarkBold \\[6pt]
    \ding{52} \\[6pt]
    \faCheck 
\end{document}

Output :

If you want to use this symbol in a web document, it is best to use the fontawesome package.

Because the fontawesome is the icon library. You can insert the same symbol into a web document using a third-party script without the help of latex.