Simon Willison’s Weblog

viewport-preview (via) I built a tiny tool which lets you preview a URL in a bunch of different common browser viewport widths, using iframes.

Posted 26th July 2022 at 12 am

Recent articles

I think "agent" may finally have a widely enough agreed upon definition to be useful jargon now - 18th September 2025
My review of Claude's new Code Interpreter, released under a very confusing name - 9th September 2025
Recreating the Apollo AI adoption rate chart with GPT-5, Python and Pyodide - 9th September 2025

css 229 iframes 21 mobile 40 projects 497 testing 63

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