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A little-understood corner of Unicode is its handling for bidirectional text (The spec is a little dry). While English languages are read left-to-right, plenty of scripts (notably Arabic and Hebrew) are read from right to left. When only a single direction of text is used in a document, it's fairly straight forward, but when texts with different directions are mixed in one document, some difficulty arises in determining direction. This document attempts to explain how bidirectional text in Unicode works and what this means for the web.