kableExtra is an R package for easily producing complex HTML/LaTeX tables, which are usually essential in a reproducible research workflow. This package extends the widely-used kable function from knitr and introduces additional functionalities such as striped-row-color or grouped column/row headers. Format specifications, including font face and color, on rows, columns and cells are also supported. The ultimate goal of kableExtra is to help users focus more on content and less on format. By design, this package provides a unified high-level interface to different formatting tools in both HTML and LaTeX but requires little knowledge of the details of either. Therefore, users can customize tables regardless of formats, in a language they are familiar with. In addition, kableExtra adopts the pipe operator (%>%) from the magritter package so users can modify tables step by step using the same logic a person uses when thinking about configuring a table. Comparing with traditional one-for-all table functions, this design is more literal and helps users customize complex tables in an easy way.