📝 Markdown Previewer
Preview Markdown in real-time. Write Markdown on the left, see rendered HTML on the right.
📋 When to Use the Markdown Previewer
This tool shows you exactly how your Markdown will look when rendered — in real time, as you type. Real scenarios where live preview saves time and catches formatting errors:
- README and documentation writing: Before pushing to GitHub, preview your README.md to verify headings, code blocks, tables, and links render correctly. Catch broken formatting before it goes live — no commit-edit-push cycle.
- Blog and article drafting: Many static site generators (Jekyll, Hugo, Astro) use Markdown for content. Preview your posts locally, check image embeds, and refine formatting without a full build step.
- GitHub comment and issue formatting: Craft well-formatted bug reports, feature requests, or code review comments with code blocks and task lists. Preview before posting to avoid formatting mistakes in public threads.
- Learning Markdown syntax: If you're new to Markdown, type on the left and see the rendered result on the right instantly. Experiment with headings, lists, bold, italic, links, images, and tables — the live feedback makes learning fast.
- Static site content preparation: When building a site with Markdown-based content (Hugo, 11ty, Next.js MDX), preview individual pages to ensure frontmatter, embeds, and internal links render as expected.
- Quick formatting check: Copy-paste any Markdown snippet to verify it's well-formed — catch missing closing tags, broken link syntax, or misaligned table columns before sharing.
The preview updates on every keystroke. No signup, no build step — just type and see.
⚙️ How the Markdown Previewer Works
The previewer uses a three-step pipeline that runs entirely in your browser:
- Parse Markdown → HTML: The marked.js library reads your Markdown text and converts it to HTML. It supports the full GitHub Flavored Markdown (GFM) specification — headings, bold/italic, ordered and unordered lists, links, images, fenced code blocks with language hints, tables, blockquotes, task lists, and strikethrough.
- Sanitize HTML: The DOMPurify library cleans the HTML output. It strips potentially dangerous content —
<script>tags, event handlers likeonerrororonclick, andjavascript:URLs. This prevents cross-site scripting (XSS) attacks: even if someone pastes malicious Markdown, the preview remains safe. - Render to preview pane: The sanitized HTML is written directly to the right-hand panel. The preview updates on every
inputevent — real-time as you type, no button click needed.
The pipeline is: marked.parse(markdown) → DOMPurify.sanitize(html) → preview pane. Both marked.js and DOMPurify are loaded from a CDN (jsdelivr). After loading, all processing stays in your browser — your Markdown is never sent to any server.
How to Use the Markdown Previewer
- Write Markdown on the left — type or paste Markdown syntax. The editor comes pre-filled with common examples: headers, bold, italics, code, lists, and blockquotes.
- See rendered HTML on the right — the preview updates in real time as you type, showing exactly how your Markdown will look when rendered.
- Experiment with syntax — try different Markdown features: tables, links, images, task lists, and code blocks with syntax highlighting. The preview is instant.
- Copy the rendered output — once satisfied, copy the raw Markdown to use in your README, documentation, blog post, or any Markdown-supported platform like GitHub, Notion, or Obsidian.
Frequently Asked Questions
What Markdown features are supported?
The previewer uses marked.js in its default GitHub Flavored Markdown (GFM) mode. Supported syntax includes: headings (# H1 through ###### H6), bold and italic, ordered and unordered lists, inline code and fenced code blocks with language hints, links and images, tables with alignment, blockquotes, task lists (- [ ] / - [x]), strikethrough, and inline HTML. Emoji shortcodes (e.g. :smile:) are not supported by marked.js by default.
Is the preview safe from malicious input?
Yes. The previewer uses DOMPurify to sanitize the HTML output from marked.js. Even if someone pastes Markdown containing embedded <script>alert(1)</script>, <img onerror=...> event handlers, or javascript: URLs, DOMPurify strips these before the content reaches the preview pane. This prevents cross-site scripting (XSS) — the preview is safe to use with untrusted Markdown input.
Is my Markdown content sent anywhere?
No. All parsing (marked.js) and sanitization (DOMPurify) happens entirely in your browser. Your Markdown text never leaves your device — it is not uploaded, stored, or transmitted to any server. The tool has no backend.
Does it work without internet?
Not on first load. The tool depends on two libraries loaded from a CDN: marked.js (for parsing) and DOMPurify (for sanitization). You need an internet connection for the initial page load to download these. After the libraries are cached by your browser, subsequent visits work without internet — the actual Markdown rendering runs entirely in your browser with no data sent anywhere.
Why does my Markdown render differently on GitHub?
Different platforms use different Markdown parsers. GitHub uses cmark-gfm (their own C-based GFM parser), while this previewer uses marked.js (JavaScript). Most basic syntax — headings, lists, code blocks, links — renders identically. Edge cases like deeply nested lists, specific table formatting, or raw HTML handling may vary slightly. For GitHub-specific previews, use the Preview tab in GitHub's own editor.
Is there a limit on input size?
No hard limit, but very large documents (10,000+ lines) may cause a noticeable delay since the preview re-renders on every keystroke. For documents over a few thousand lines, consider splitting into sections or using a local Markdown editor. The preview runs synchronously in the browser — extremely large inputs may briefly freeze the tab.