01Direction is structural, not cosmetic
Build with logical properties — start and end rather than left and right — from the first component. Retrofitting direction into a finished interface is far more expensive than designing for it.
Icons with direction, progress indicators and animations all need mirroring rules decided once, centrally.
02Typography deserves real attention
Arabic needs different line height, letter spacing and font weight to feel balanced next to a Latin heading. Reusing the Latin scale unchanged is why so many Arabic interfaces look cramped.
Keep numerals, codes and phone numbers in a consistent direction so they never reorder unexpectedly inside a sentence.
03Content is not a string table
Arabic copy is rarely the same length as English, and a direct translation of marketing copy usually reads as machine output. Write for the audience in each language, with the same intent rather than the same words.
Plan layouts for expansion and contraction so neither language looks like the afterthought.
04Make language part of the URL
Serve each language on its own path with hreflang alternates. It is better for search engines, it makes links shareable, and it removes the flicker of client-side switching.