Boxscore data is built off of Retrosheet data. Retrosheet provides, free of charge, both Games-level attributes and play-level data that can be rolled up into Boxscores, game logs, extended stats and batting/pitching splits.

The Baseball Cube leverages this data to populate data in several different sections of the site. Pages where Retrosheet data is used are mostly indicated and if they aren't the footer of every page explains that boxscore-level data is from Retrosheet.

The granularity of the data from Retrosheet provides is short of statcast but does provide game states and fielders for every play since 1957.