Simon Willison’s Weblog

What is a Polyfill? Useful new term: a Polyfill is “a shim that mimics a future API providing fallback functionality to older browsers”.

Posted 9th October 2010 at 11:48 am

Recent articles

GPT-5: Key characteristics, pricing and model card - 7th August 2025
OpenAI's new open weight (Apache 2) models are really good - 5th August 2025
ChatGPT agent's user-agent - 4th August 2025

browsers 85 recovered 213 polyfill 2 remy-sharp 3

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