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Public story · 2026-08-17 · high
The August 16 tool update skips servers entirely, so platforms that block animated SVG will still take the file.
Why now: This lands now because sharing surfaces still won't render animated SVG natively, forcing workarounds like this one.
Willison shipped browser-side video export for animated SVG on August 16, per simonwillison.net. Plenty of platforms won't render an animated SVG in a feed or a chat window, but they'll play an MP4 without complaint. LLMs make animated SVGs easy to generate, which raises the odds someone wants to share one somewhere it won't render.
The tool detects whether an SVG has SMIL or CSS animation, then guesses the loop duration. It renders the frames and hands them to ffmpeg.wasm, which compiles an MP4 entirely in the browser. No server, no upload step. The commit is verifiable in simonw/tools as 73e0327, per simonwillison.net.
This is a patch on a platform problem, not a fix to the format itself. The SVG format works fine. The tool exists because sharing surfaces refuse to render it. As more people generate throwaway animations with LLMs, expect more conversion shims like this one. A client-side export tool ships in a day. A platform format change does not.
The source doesn't say how long the ffmpeg.wasm compile takes for longer animations, or whether the loop-duration guess ever misfires on irregular timing.
Each link below shares sources, entities, or timing with this story.
Simon Willison released LLM / Shared entities / Same source domain / Earlier coverage
Linked by a graph relationship (Simon Willison released LLM); both cover LLM, Simon Willison, SVG; reported by the same outlet (simonwillison.net).
CORS Chat built by Simon Willison / Shared entities / Same source domain / Earlier coverage / Tension
Linked by a graph relationship (CORS Chat built by Simon Willison); both cover Simon Willison, SVG; reported by the same outlet (simonwillison.net).
Simon Willison released LLM / Shared entities / Same source domain / Earlier coverage / Tension
Linked by a graph relationship (Simon Willison released LLM); both cover LLM, Simon Willison; reported by the same outlet (simonwillison.net).
Linked by a graph relationship (Simon Willison released LLM); both cover LLM, Simon Willison; reported by the same outlet (simonwillison.net).
Linked by a graph relationship (Simon Willison released LLM); both cover LLM, Simon Willison; reported by the same outlet (simonwillison.net).
Linked by a graph relationship (Simon Willison released LLM); both cover Simon Willison, SVG; reported by the same outlet (simonwillison.net).
Simon Willison released LLM / Shared entities / Same source domain / Earlier coverage
Linked by a graph relationship (Simon Willison released LLM); both cover LLM, Simon Willison; reported by the same outlet (simonwillison.net).
Linked by a graph relationship (Simon Willison released LLM); both cover LLM, Simon Willison; reported by the same outlet (simonwillison.net).