If so, it appears that rendering on GitHub.com has `display:inline-block` for `<summary>` tags and looks like this: <img width="188" alt="image" src="https://github.com/github/jekyll-commonmark-ghpages/assets/1041752/94efc2d9-36c8-4189-a1fc-07b92cc2c173"> And on GitHub Pages + Jekyll with `markdown: GFM` processor it turns out as <img width="167" alt="image" src="https://github.com/github/jekyll-commonmark-ghpages/assets/1041752/ce62c722-b0af-4ff2-ad1b-272d7de015bd"> Adding ```yaml markdown: CommonMarkGhPages commonmark: options: ["UNSAFE", "SMART", "FOOTNOTES"] ``` does not help The code is: ```html <details> <summary> # Header </summary> Para*graph* </details> ``` How can I render this in GitHub Pages to be identical to github.com? @anticomputer Or should this issue be transferred to https://github.com/github/cmark-gfm/issues , if it's more relevant there? Thanks :)