Markdown to HTML Converter

The Markdown-to-HTML converter takes the most common authoring workflow on the modern web — write in Markdown, publish as HTML — and makes it instant. Paste any Markdown into the left pane and the right pane shows the rendered HTML in real time. No server roundtrip, no signup, no file upload: marked.js runs entirely in your browser, parsing Markdown into clean HTML in milliseconds. Use it for one-off README conversion, blog draft preview, CMS migration between platforms with different Markdown dialects, or quick verification that your syntax is correct before committing to a static-site generator. Supports the full CommonMark spec plus GitHub Flavored Markdown extensions (tables, task lists, strikethrough, autolinks) — meaning what works on GitHub will work here without surprises.

Step 1: Paste your Markdown text into the left input pane. The converter accepts any length from a single line to thousands of lines of content. Standard CommonMark syntax works: `#` for headings, `*text*` for italic, `**text**` for bold, `` `code` `` for inline code, `[link](url)` for links, `-` or `*` for unordered list items, `1.` for ordered lists, `>` for blockquotes, triple-backtick for fenced code blocks. Step 2: Watch the right pane render HTML in real time as you type or paste. Tables render with proper borders, headings get auto-generated `id` attributes (for anchor links), code blocks preserve language tags, and inline HTML passes through. Step 3: Click Copy HTML to grab the raw HTML source for pasting into a `.html` file, CMS rich-text editor, or static-site template. Click Copy Rendered to copy the formatted view if your target supports rich text (Word, Google Docs, email composers).

This converter has both enabled by default. CommonMark (2014) is the standardized, unambiguous Markdown spec that defines exact parser behavior — adopted by GitHub, Reddit, Stack Overflow, Discourse, and most modern tools. GitHub Flavored Markdown (GFM) extends CommonMark with five additions: tables (pipe-separated rows with alignment), task lists (`- [ ]` and `- [x]` for checkboxes), strikethrough (`~~text~~`), autolinks (raw URLs become clickable without explicit `[](url)` syntax), and restricted raw HTML (some tags filtered for security). Since GitHub READMEs are the most common Markdown source on the web, GFM compatibility is essential — this converter renders exactly what GitHub renders for the same input. If you need pure CommonMark output (no GFM extensions), you can disable GFM in the options menu, but the default works for 95% of use cases.

GFM tables use pipe characters (`|`) to define columns and hyphens (`-`) in the header separator row. Basic syntax: `| Name | Age |\n|------|-----|\n| Alice | 30 |`. Column alignment is encoded in the separator row: `-:` for right, `:-:` for center, `:-` or `-` for left (default). Example with alignment: `| Tool | Speed | Free |\n|:-----|------:|:----:|` produces a 3-column table with Tool left-aligned, Speed right-aligned, Free center-aligned. The renderer outputs proper `<table>`, ``, ``, `<tr>`, `<th>`, `<td>` elements with inline `style="text-align:..."` attributes for the alignment. Pipes at the start and end of each row are optional but commonly added for readability. Column widths in the source don't need to align — the parser doesn't care about visual spacing.

Fenced code blocks use triple backticks (or tildes) to open and close: ```\ncode here\n```. Add a language hint after the opening fence to enable syntax highlighting when the HTML is published: ```javascript or ```python or ```bash. The converter outputs `<pre><code class="language-X">` where X is the language name. This converter does not apply syntax colors itself — coloring is done by a separate library like highlight.js, Prism.js, or Shiki when the HTML is rendered on your page. Why split? Syntax highlighting libraries are 50KB-200KB each and add significant page weight; the converter stays lean by outputting only the language tag and letting your publishing pipeline add colors. Common language tags: javascript, typescript, python, java, csharp, go, rust, ruby, php, html, css, json, yaml, xml, bash, sql, markdown.

The split-pane interface — Markdown source on the left, HTML preview on the right — is the standard authoring workflow for technical writers and developers. It lets you write in the lightweight, readable Markdown format while immediately seeing the published-looking result. Compared to WYSIWYG editors (Word, Google Docs): Markdown is faster to write (no mouse-reaching for formatting buttons), version-controllable (plain text diffs cleanly in Git), portable (any text editor works), and produces clean HTML without bloated nested divs. Compared to writing HTML directly: Markdown is 3-5x faster for typical content (headings, paragraphs, lists, links), reads naturally in source form, and removes formatting decisions from the writing flow. Use Markdown for any text-heavy content; switch to HTML only when you need fine-grained presentation control.

The converter outputs semantic HTML5 — elements that describe content meaning, not just appearance. Headings become `<h1>` through `<h6>` with auto-generated `id` attributes for anchor linking. Paragraphs become `<p>`. Bold becomes `<strong>` (not `<b>`), italic becomes `<em>` (not `<i>`) — semantic equivalents that work better with screen readers and CSS targeting. Unordered lists become `<ul><li>`, ordered lists `<ol><li>`. Blockquotes become `<blockquote>`. Code spans become `<code>`, fenced blocks become `<pre><code>`. Links become `<a href>`. Images become `<img src alt>`. The result is clean, accessible HTML that drops into any modern CMS, static site generator, or HTML file without modification. No inline styles (except table alignment), no extra `<div>` wrappers, no class attributes (except language tags on code blocks).

README files are the most common Markdown source on the web — every GitHub repository has one, most package registries (npm, PyPI, RubyGems) render them automatically. To convert a README.md for a documentation site, paste the file contents into the converter and copy the HTML output. Common adjustments after conversion: (1) Relative links — README files often use relative paths (`./docs/install.md`); rewrite to absolute URLs for the published site. (2) Image paths — same issue, README images use `./images/logo.png`; update to the published image URL. (3) Anchor IDs — auto-generated heading IDs use lowercase-hyphen format (`Installation` becomes `id="installation"`); update internal anchor links accordingly. (4) Repository-specific syntax — GitHub auto-links issue references like `#123` and user mentions like `@username`; these don't auto-link outside GitHub, rewrite as explicit links if needed.

Static site generators (SSGs) process Markdown files into HTML pages at build time, so manual conversion isn't usually needed — you commit `.md` files to your repo and the SSG handles the rest. Common SSGs and their Markdown handling: Jekyll (Ruby) uses kramdown by default, CommonMark-compatible with some GFM. Hugo (Go) uses Goldmark, full CommonMark + GFM + extensions. Next.js MDX (JavaScript) uses remark/rehype, lets you embed React components in Markdown. Eleventy (JavaScript) uses markdown-it by default. Astro (JavaScript) uses remark and supports MDX. Gatsby (JavaScript) uses gatsby-plugin-mdx with remark. This converter is most useful for: (a) one-off conversions outside an SSG workflow, (b) verifying that your Markdown renders correctly before committing, (c) migrating content between SSGs that use different Markdown dialects.

Six common gotchas. (1) Soft line breaks inside paragraphs — single newlines collapse into spaces per CommonMark, not `<br>`. Use two trailing spaces or a blank line for an explicit break. (2) Indented code blocks (4-space indent) vs fenced (triple-backtick) — both work, but fenced is recommended because it preserves language tags. (3) Nested lists with wrong indentation — CommonMark requires 2 or 4 spaces, mixing tabs and spaces breaks rendering on some parsers. (4) Inline HTML stripped by stricter renderers — GitHub and Reddit filter many tags for security; what works in this converter may not work everywhere. (5) Headings without blank line before/after — most parsers tolerate, but CommonMark recommends blank lines for clarity. (6) Strikethrough with single tildes — single-tilde doesn't work, needs `~~double tildes~~`. When debugging, check what dialect the target platform speaks (CommonMark? GFM? something custom?) before assuming the converter is wrong.

This converter runs 100% in your browser — your Markdown text never leaves the page. Server-side Markdown converters typically log every conversion for analytics and may store input for caching or error monitoring. For most casual conversions this isn't a problem, but developers and technical writers regularly paste content that should not leak: API keys in code samples, internal documentation, proprietary technical specs, draft blog posts under NDA, customer data in support documentation. Client-side conversion eliminates the leak risk entirely. To verify: open browser DevTools Network tab, paste Markdown, click convert — you'll see zero outbound requests during the conversion. The marked.js library loads once when the page opens (visible in initial page load); after that, all conversion is local. For untrusted Markdown input from third-party sources, sanitize the rendered HTML with DOMPurify before injecting into a page to prevent XSS attacks.

Quick syntax reference. Headings: `# H1` through `###### H6`. Bold: `**text**`. Italic: `*text*` or `_text_`. Bold+italic: `***text***`. Strikethrough (GFM): `~~text~~`. Inline code: `` `code` ``. Link: `[text](https://url.com)`. Image: ``. Auto-link (GFM): `https://example.com` (raw URL, no brackets). Unordered list: `- item` or `* item` or `+ item`. Ordered list: `1. item`. Nested list: indent with 2 spaces. Blockquote: `> quoted text`. Multi-line quote: prefix every line with `>`. Fenced code block: triple backticks (open and close) with optional language tag. Indented code block: 4 spaces or 1 tab at line start. Horizontal rule: `---` or `***` on its own line. Table (GFM): `| col1 | col2 |\n|------|------|\n| val1 | val2 |`. Task list (GFM): `- [ ] todo` and `- [x] done`. HTML pass-through: any HTML tag works inline. Hard line break: two trailing spaces. Escape special character: backslash before, e.g. `\*not italic\*`. Use the converter for any case that confuses you — the live preview shows exactly how each pattern renders.