Version 1.0 was published and printed in January 2019, designed by Carlos Pérez Cerón, with María González de Cossío as the editor.

Version 2.0 has some edits based on feedback from Kevin Larson: a reference to CAPTCHAs is removed; the results of studies on ClearType are clarified; letter frequency is included as a further factor in legibility; a distinction is made between critical type size and optimal type size; a more recent study on letter, word, and line spacing is added; earlier research on disfluency is included. This version was further revised for presentation on this website; the project is sponsored by Google Fonts, produced by Rosetta Type, and implemented by Johannes Neumeier.