Simon Willison’s Weblog

Understanding Bidirectional (BIDI) Text in Unicode. It turns out you need to sanitise user input to ensure there are no unicode characters that switch your site’s regular text to RTL.

Posted 15th March 2009 at 4:37 am

Recent articles

Introducing gisthost.github.io - 1st January 2026
2025: The year in LLMs - 31st December 2025
How Rob Pike got spammed with an AI slop "act of kindness" - 26th December 2025

bidi 1 cal-henderson 7 filtering 2 security 571 unicode 29 userinput 1

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