Simon Willison’s Weblog

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16th October 2025

Tool OpenAI Prompt Caching Playground — Explore OpenAI's prompt caching feature by testing different prompt structures and observing cache hit rates across multiple requests. This interactive playground lets you compose system instructions, document context, and user questions, then send them to the Chat Completions or Responses API to track how cached tokens reduce costs and improve performance.
Posted 16th October 2025 at 5:04 pm

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