overleaf table size length of text
% Makes table with = text width
\documentclass{article}
\usepackage{graphicx}
\begin{document}
\noindent\hrulefill
\smallskip\noindent
\resizebox{\linewidth}{!}{%
\begin{tabular}{r|lll}
\multicolumn{1}{r}{}
& \multicolumn{1}{l}{Heading 1}
& \multicolumn{1}{l}{Heading 2}
& \multicolumn{1}{l}{Heading 3} \\ \cline{2-4}
Row 1 & Cell 1,1 & Cell 1,2 & Cell 1,3 \\
Row 2 & Cell 2,1 & Cell 2,2 & Cell 2,3
\end{tabular}}
\end{document}