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Markdown Previewer

preview Markdown with live side-by-side rendering

By Bikram NathLast updated

A markdown previewer renders your raw .md source into formatted HTML in real time as you type, letting you catch broken table alignment, missing blank lines before lists, or stray asterisks before they hit a PR. Paste a README with a pipe-delimited table on the left and watch the rendered columns appear on the right instantly. Unlike a static file viewer, edits reflect immediately without a save-reload cycle.

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What is Markdown Previewer?

A Markdown Previewer takes raw Markdown text and renders it as formatted HTML side by side, updating as you type. Paste a README draft containing a fenced code block and a pipe table, and the right panel shows immediately how headings, bold text, and column alignment will appear when the file is viewed on GitHub or processed by a static site generator like Jekyll.

Developers reach for this instead of VS Code's built-in preview (Cmd+Shift+V) when working outside their editor, reviewing doc copy shared over Slack, or checking that Markdown pasted from Notion still renders cleanly. Dillinger and StackEdit are fuller alternatives that add cloud saves, file imports, and export flows. This tool skips that overhead when you only need to verify a render.

The critical practical detail is Markdown flavor. CommonMark and GitHub Flavored Markdown differ on several points: GFM adds task-list checkboxes (- [ ]), strikethrough via double tildes, and auto-linked bare URLs, and it allows tables without a preceding blank line. If the previewer uses a strict CommonMark parser, a GFM-style table without that blank line may fail to render here but display correctly on GitHub, making your local editor preview more authoritative for GitHub-targeted content.

When to use Markdown Previewer

✓Verify that a README table renders with correct column widths before opening a pull request in a new repo.
→Check Markdown copied from a Confluence export for stray HTML entities or broken heading levels before pasting into GitHub Issues.
⚡Draft changelogs in CHANGELOG.md format and confirm that ordered lists, code spans, and blockquotes display as expected.

Frequently Asked Questions

Does this render GitHub Flavored Markdown or CommonMark, and does it matter for my README?
The distinction matters specifically for tables, task lists, and auto-linked URLs. CommonMark does not include those features; GFM adds them as extensions. If you write '- [ ] item' expecting a checkbox, a CommonMark renderer will show it as plain text. For README files destined for GitHub, the most reliable check is GitHub itself. This tool is most useful for catching issues that exist in both flavors: missing blank lines before headings, unclosed bold markers, or code fences using an unrecognized language identifier.
Why does raw HTML embedded in my Markdown not render, or get stripped entirely?
Most Markdown parsers pass inline HTML through to the output, but browser-based previewers typically sanitize the result using a library like DOMPurify to prevent XSS. Tags like script, iframe, and style get stripped before the HTML hits the DOM. A div or span with a class attribute usually survives; a script tag will not. If exact HTML passthrough is critical, a local pandoc conversion is more predictable than any browser-based previewer, because pandoc applies no sanitization by default.
How does this handle YAML front matter, the --- block at the top of Jekyll and Hugo files?
YAML front matter is not part of the CommonMark or GFM specification. Parsers that are front matter-aware, like gray-matter, strip the block before rendering. Parsers that are not will treat the opening --- as a setext-style heading rule or a thematic break, and the key-value lines will appear as body text. If your file opens with '--- title: My Post ---' and you see those lines rendered in the output, the parser has no front matter support. Strip the block before pasting to check only the actual content formatting.
Why does my fenced code block render correctly but show no syntax highlighting?
The language identifier after the opening fence, for example three backticks followed by python or bash, is advisory. Markdown itself defines no coloring. GitHub applies Linguist-based highlighting server-side; static site generators delegate to Prism or Highlight.js on the client. A Markdown previewer that loads no syntax highlighting library produces a semantically correct pre/code element with no color applied. The rendered HTML is accurate; the coloring is a presentation layer that only appears if the host environment explicitly wires up a highlighter library.
Can I preview a Markdown file that uses relative image paths like ./images/photo.png?
Relative image paths will not resolve in a browser-based previewer because there is no local filesystem context. The src attribute resolves against the page's URL, not your project directory, so the image request fails silently. Images referenced by absolute HTTPS URLs load normally. For checking image-heavy READMEs with relative paths, VS Code's built-in Markdown preview has filesystem access and handles them correctly, as does grip, a Python tool that renders Markdown using the GitHub API and serves it locally with full path resolution.

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