Minimum recquirements
For body text:
Make sure body texts are at least 16px* when working @1x. Use a highly legible typeface, preferably a sans-serif one. If you use a highly stylised typeface, provide an option to switch to a more legible typeface for everyone. For left-to-right language, always left-aligned the content. For right-to-left language, always right-aligned the content. Set the line-height at 1.5 the size of the body text. Use sentence case (avoid full caps or full italic). Keep each line to no more than 70 characters. *This reference size is for tools like Figma or Photoshop working @1x. It means that the frame/artboard size is at 640 x 360 pixels, not points. Multiple these values by 2 or 3 if you are working @2x (@720px) or @3x (@1080px). Finally, make sure to find the right equivalent when integrating as engines and tools within engines may have units that differ.