Kurtuluş Mert Küçük¹ (), Rashid Md Mamunur², Veronica Penkova³, Amy Giroux⁴, Nilsu Atılgan⁵, Shaun Wallace⁶, Sam Berlow⁷, Anna Kosovicheva⁸, Stephanie Day⁹, Ben D. Sawyer¹⁰; ¹University of Central Florida, ²University of Toronto, ³University of Rhode Island

We introduce a scientific tool designed for online reading performance studies. Tool assesses optimum reading format for individuals by allowing experimenters to manipulate various text parameters. Developed using psychophysical research, the tool utilizes online testing via Pavlovia and Psychopy, enabling large-scale participant testing with reduced environmental noise and increased external validity. Our tool’s primary function is to assess reading performance across various typefaces, font parameters (e.g., weight, width, etc.), letter spacings by ranking comprehension scores and reading speed. The tool focuses on paragraph reading (approximately 150-word paragraphs), though it can also evaluate other forms of reading such as single word recognition and sentence reading. Stimuli are presented as .jpg images of texts with `modified fonts or spacings. Using images of texts instead of directly rendering using the browser, prevents potential incompatibility problems across different monitors while manipulating letter spacing and axes of variable fonts. We outline the methodology, emphasizing the tool's reliance on automatic randomization and counterbalancing, and the creation of stimulus sets. We provide a pilot study as an example to explain the configuration of tool’s settings and how counterbalancing functions. Example also outlines how behavioral performance measures such as comprehension scores, reading speed calculations (as words per minutes), and experimental conditions are registered in the data file. Overall, we provide an overview of the tool's design, functionality, and potential to expand the capabilities of online readability studies.