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

Claude Opus 4.5, and why evaluating new LLMs is increasingly difficult - 24th November 2025
sqlite-utils 4.0a1 has several (minor) backwards incompatible changes - 24th November 2025
Olmo 3 is a fully open LLM - 22nd November 2025

css 229 iframes 21 mobile 40 projects 507 testing 64

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