Unlike other text-fitting tools like FitText.js, Font‑To‑Width does not scale the font-size (at least not by default). Instead, it chooses a width or weight variant according to what fits best, and then allows for letter- and word-spacing adjustments as needed.
Font-To-Width is meant for headlines and other short pieces of text. It was not built for justifying multi-line body type. Due to its use of micro spacing adjustments, Font-To-Width works best in browsers like Chrome, where subpixel spacing is supported. Other browsers that round spacing to integer values will show rounding errors.Font-To-Width