Full GFM, Not Just Basic Markdown
A previewer that only supports the original CommonMark spec will render a Markdown table or a task-list checkbox as plain, broken-looking text — which is exactly the content most READMEs and documentation actually use. This tool supports GitHub-flavored Markdown specifically, so tables, task lists, and strikethrough all render the way they actually look on GitHub, alongside a live word count and a copy button for the rendered HTML itself.