Right-to-left

Also called RTL, bidi, bidirectional text

Scripts written right to left — Arabic, Hebrew, Persian, Urdu. Text is stored in logical order and reordered for display by the Unicode bidirectional algorithm (UAX #9), which is where mixed-direction runs go wrong: a Latin product name or a phone number inside an Arabic sentence needs isolation or it will reorder around punctuation.

One Arabic sentence containing a Latin product name and a phone number, shown three times. First in storage order, reading left to right; then reordered for display, the Arabic running right to left with the Latin run held left to right inside it; then the same without isolation, where the trailing punctuation and digits have jumped to the wrong side of the Latin name.

In practice

Mirroring a layout is the easy half. Arabic also needs contextual joining, more line height for its ascenders and descenders, and larger sizes for equivalent legibility — a Latin type scale applied unchanged reads small.

Not to be confused with

CJKChinese, Japanese and Korean typesetting. Characters occupy a fixed em square, so text sets to an even grid; there are no word spaces, so lines may break almost anywhere; and a usable font runs to tens of thousands of glyphs, which makes it megabytes and makes unicode-range subsetting mandatory rather than an optimisation.

How this term connects

Related Confused with

In practice

Not to be confused with

Related

How this term connects

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