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FAPersian
March 2, 2026

Bilingual design systems: a working method

RTL is not LTR mirrored. A method for building systems that treat each language as a first-class user, not a translation.

By Mehdi Gerami · 1 min read

When a product launches in Persian after launching in English, the result is usually a mirror. Mirrors are cheap. They also lie — Persian is not English in reverse. Its display faces have different x-heights, different counters, different breathing.

Three principles

  1. Type metrics first. Pair display faces by baseline and x-height, not by aesthetic resemblance.
  2. Logical properties everywhere. margin-inline-start is not a flourish.
  3. Test in the second language before declaring the system done.