Simon Willison’s Weblog

OCR and Neural Nets in JavaScript. John dissects the brilliant Greasemonkey script that solves simple captchas using the canvas element and HTML5’s getImageData API.

Posted 25th January 2009 at 12 am

Recent articles

The last six months in LLMs, illustrated by pelicans on bicycles - 6th June 2025
Tips on prompting ChatGPT for UK technology secretary Peter Kyle - 3rd June 2025
How often do LLMs snitch? Recreating Theo's SnitchBench with LLM - 31st May 2025

getimagedata 1 captcha 6 ocr 22 javascript 711 greasemonkey 54 canvas 38 john-resig 32

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