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

First impressions of Claude Cowork, Anthropic's general agent - 12th January 2026
My answers to the questions I posed about porting open source code with LLMs - 11th January 2026
Fly's new Sprites.dev addresses both developer sandboxes and API sandboxes at the same time - 9th January 2026

css 231 iframes 21 mobile 40 projects 515 testing 67

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