Simon Willison Adds MP4 Export to Markdown SVG Renderer Tool
Developer Simon Willison added MP4 video export to his markdown-svg-renderer tool on 16 August 2026, letting users convert animated SVGs into shareable videos entirely inside the browser.
👁 116 reads
Developer Simon Willison has enhanced his markdown-svg-renderer tool with MP4 video export capability, announced on 16 August 2026. This browser-based utility helps users convert Markdown documents that contain SVG graphics into multiple formats, now including video files that can be easily shared across platforms that don’t support animated SVGs natively.
- The tool now converts animated SVGs to MP4 by rendering animation frames and compiling them with ffmpeg.wasm running in the browser
- The MP4 export loads more than 30MB of WebAssembly-compiled FFmpeg to process frames client-side, with no server involved
- Earlier tabs already supported PNG and JPEG export; the tool also accepts GitHub Gist URLs to produce bookmarkable rendered pages
What the Markdown SVG Renderer Tool Does
The markdown-svg-renderer is a web-based tool that takes Markdown documents containing SVG blocks and renders them into an interactive, tabbed display. SVG stands for Scalable Vector Graphics, a format commonly used for diagrams, charts, and illustrations that can include animations. Markdown is a lightweight markup language widely used by developers and writers to format text documents.
The tool originally launched in May 2026 with PNG and JPEG export options, allowing users to convert vector graphics into standard image formats that can be rasterised in the browser. Users can either paste Markdown directly into the tool or provide a CORS-friendly URL or GitHub Gist link. When using a URL, the tool creates a bookmarkable page that embeds the source URL directly into the web address, making it easy to return to specific conversions.
How the New MP4 Export Feature Works
The newly added MP4 tab addresses a common frustration for anyone working with animated SVGs: many social media platforms, messaging apps, and content management systems cannot display animated SVG files properly, but they handle MP4 video files without any problems. This creates a practical sharing barrier for developers and designers who want to showcase animated graphics.
The MP4 export process happens entirely within your web browser. First, the tool examines the SVG file to detect any animations. It then attempts to estimate the correct loop duration for the animation. Next, it renders multiple frames of the animation sequence. Finally, it loads ffmpeg.wasm, which is FFmpeg compiled to WebAssembly, weighing in at over 30 MB. FFmpeg is a powerful multimedia framework used for video processing, and WebAssembly allows it to run directly in the browser without requiring server-side processing or software installation. The tool then assembles all the rendered frames into a complete MP4 video file that you can download and share.
What This Means for AI and Development Workflows
This enhancement is particularly useful for developers and technical communicators who generate diagrams and visualisations, including those created by AI tools that output SVG format. Many AI-powered diagramming and visualisation tools produce SVG files because they’re scalable and can include interactive elements. However, when sharing these outputs in documentation, presentations, or on social media, the animated SVG format often fails to display correctly. Having a browser-based conversion tool eliminates the need for complex video editing software or command-line tools, making the workflow more accessible to non-technical users.
Google · Your sourcesQuantslant higher in your Google - one clickAdd to preferred sources →Frequently Asked Questions
When was the MP4 export feature added to the tool?
Simon Willison added the MP4 video export capability to the markdown-svg-renderer tool on 16 August 2026. The tool itself was first built in May 2026 with PNG and JPEG export options.
What formats can the markdown-svg-renderer tool export?
The tool now offers multiple export tabs: PNG and JPEG for static images, and the newly added MP4 for animated SVGs. All conversions happen directly in your browser, and files can be downloaded or copied to your clipboard.
Why would someone need to convert an animated SVG to MP4?
Many platforms cannot play animated SVG files natively, but they accept MP4 video files without issue. This makes MP4 export essential for sharing animated graphics on social media, messaging apps, and content management systems that don’t support the SVG animation format.
More on this from QUANTSLANT
ai tools·Your AI Slop Bores Me Lets Humans Pretend to Be ChatbotsA web app called Your AI Slop Bores Me pairs real people on both sides of a fake AI chat, with one person submitting prompts and another roleplaying as the model.