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

NVIDIA DGX Spark: great hardware, early days for the ecosystem - 14th October 2025
Claude can write complete Datasette plugins now - 8th October 2025
Vibe engineering - 7th October 2025

bidi 1 cal-henderson 7 filtering 2 security 553 unicode 29 userinput 1

Monthly briefing

Sponsor me for $10/month and get a curated email digest of the month's most important LLM developments.

Pay me to send you less!

Sponsor & subscribe