Markdown Runner

What Is a Markdown Runner?

Markdown is plain text with a handful of punctuation conventions that stand in for formatting: a hash for a heading, asterisks for emphasis, square brackets for a link. It is readable as source and unambiguous once rendered, which is why it powers READMEs, documentation sites, static blogs, issue trackers and note-taking apps.

A Markdown runner closes the gap between writing and seeing. You type on one side, press Run, and read the rendered document on the other — plus the HTML that a browser or CMS will actually receive.

Two Views of the Same Document

The Preview tab shows the formatted result, styled with the site's own typography so headings, lists and code blocks look the way published content looks. The HTML tab shows the generated markup itself, which is what you need when a platform accepts HTML but not Markdown — many email tools, wikis and legacy CMS editors fall into that category.

Supported Syntax

• Headings: # through ######, mapping to h1–h6.
• Emphasis: bold, italic, bold italic and strikethrough.
• Code: inline backticks and fenced blocks with an optional language label.
• Links and images: standard inline syntax, with links marked rel="nofollow noopener" and images lazy-loaded.
• Lists: ordered, unordered and task lists with checked or unchecked boxes.
• Tables: pipe-delimited with a header separator row.
• Blockquotes and horizontal rules, including nested content inside a quote.

Why the Output Is Sanitized

Markdown documents frequently arrive from elsewhere — a colleague, a repository, a support ticket. If raw HTML inside such a document were rendered as-is, a malicious file could execute script in your browser. This runner escapes raw HTML and then passes the generated markup through DOMPurify before display, so the preview cannot execute anything. That is a deliberate trade: you lose HTML passthrough and gain a preview you can trust with any file.

Writing Statistics

Word count, character count, line count and an estimated reading time at 220 words per minute update as you type. These matter for content work: a blog post with a target length, documentation that should stay skimmable, or a release note with a hard character budget.

Common Workflows

Reviewing a README before pushing it, especially tables and nested lists where a single missing character changes the output. Drafting a blog post in Markdown and exporting the HTML for a CMS that lacks Markdown support. Preparing release notes and confirming the heading hierarchy is sequential. Teaching Markdown by editing and re-rendering. Converting internal documentation into HTML for a wiki that only accepts markup.

Honest Scope

Full CommonMark and GitHub Flavored Markdown include footnotes, definition lists, autolink literals, complex nested indentation rules and HTML passthrough. This renderer implements the parts people actually use daily and stops there rather than claiming complete spec compliance. For byte-exact GitHub rendering, check your document on GitHub itself.

Privacy

Parsing, sanitising and counting all happen in your browser. Your document is never uploaded and is stored only as a local draft that Reset clears.

Convert existing documents with the Markdown to HTML Converter, measure text with the Word Counter, or tidy generated markup with the HTML Minifier.

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