Markdown is a lightweight markup language that reads naturally as plain text but renders as formatted HTML. Writing Markdown blind (without seeing the rendered output) is inefficient. A Markdown preview tool shows the formatted result alongside the source, letting you write and verify at the same time.
Where You Write Markdown
GitHub README files are the most common context. Every repository's README.md is rendered as Markdown on the repository homepage. Writing a clear, well-formatted README requires seeing how headings, lists, code blocks, and links will render.
Documentation sites (GitBook, Docusaurus, MkDocs, VuePress) are written in Markdown. Previewing while writing ensures the structure and formatting are correct before deploying.
Blog posts and static sites (Jekyll, Hugo, Eleventy) use Markdown for content. Previewing lets you catch formatting mistakes before publishing.
Notes and knowledge bases (Notion, Obsidian, Roam Research) accept Markdown input. Previewing helps you format notes for future readability.
Pull request and issue descriptions on GitHub, GitLab, and Jira support Markdown. Previewing before submitting ensures the description renders correctly.
What a Good Markdown Previewer Shows
A live preview shows the rendered output updating in real time as you type, so you can see the effect of every character. This is faster than a manual render button because you do not need to trigger the update.
Syntax highlighting for code blocks shows fenced code blocks rendered with language-appropriate colors.
Table support renders pipe-delimited table syntax as actual HTML tables.
GitHub Flavoured Markdown (GFM) support includes task list checkboxes, strikethrough text, and autolinks.
Using the DevHexLab Markdown Previewer
Open the tool at /tools/javascript/markdown-previewer. Type or paste Markdown in the left panel. The rendered preview appears in the right panel and updates as you type. Copy the Markdown when it looks correct.
Frequently Asked Questions
Can I paste HTML into a Markdown file?
Yes. Standard Markdown processors pass raw HTML through unchanged. You can mix Markdown and HTML in the same file, though mixing the two is best avoided for readability.
Write Markdown, preview instantly, publish with confidence.