BiDi

BiDi (BiDirectional) describes a document that contains both right-to-left (RTL) and left-to-right (LTR) text.

User Interfaces should display BiDi content correctly, but many fail. An example is the Hebrew translation of the name Sarah: שרה, spelled (from right-to-left) sin (ש), resh (ר), heh (ה). Many programs would display the letters in the opposite order.

It is possible to flip the left-to-right display order to a right-to-left display order, but doing this sacrifices the ability to display BiDi scripts correctly — at least one is always incorrectly displayed. With bidirectional script support, it is possible to mix characters from different scripts on the same page, regardless of writing direction.