Zerdly

Markdown to HTML Converter

Converts Markdown source into HTML with a live preview.

100% FreeRuns in your browserBasic
How to use this calculator

Markdown

Dialect

Result

Type or paste Markdown.

Runs entirely in your browser. Your input is not uploaded or stored.

How the method works

Raw text and protected preview are separate outputs
Illustrative method
Raw text and protected preview are separate outputsFlow: input text or file, parsed locally in an inert document, converted, then split into two outputs — the raw converted text for copy or download, and a sanitised preview shown in a sandbox with no network access.Input text or filestays on your deviceParse locallyno scripts, no fetchConvertescape · map structureRaw output textcopy or downloadSanitise → previewsandboxed, no networkexport deliberately
Parse locally (nothing is fetched or run) → convert → two separate outputs: the raw text you copy or download as written, and a sanitised preview in a sandboxed frame with scripts and network blocked. Downloading is always a deliberate click.

The HTML you copy and the preview are separate: the preview is sanitised again and sandboxed, and fenced code always stays literal text. Fixed example values for illustration — not your result.

How to use this calculator

  1. Paste Markdown and choose GFM or CommonMark core, raw-HTML handling, heading IDs, optional local code colouring, and a fragment or complete document.
  2. Check the protected preview, or switch to the HTML code view.
  3. Copy the fragment or the complete document, or download it as .html.

How it works

Headings, paragraphs, emphasis, code, fenced and indented code blocks, blockquotes, nested lists, links, images and (in GFM) tables and strikethrough are converted, with all text escaped. Raw HTML is shown as text unless you allow it.

Links and images must use http(s), mailto, tel, a fragment or a relative path; javascript: and other schemes are removed and listed. Fenced code always stays literal.

The preview is sanitised with an allowlist and shown in a sandboxed frame that cannot run scripts or load anything — images appear as placeholders. The complete document uses a small built-in stylesheet, not a CDN. Code colouring, when on, is a small built-in tokeniser for common languages: the code text is unchanged and stays escaped.

Worked example

# Hi. becomes <h1>Hi</h1>. A fenced <script> stays as escaped code, and [x](javascript:…) loses its link.

Common mistakes

  • Allowing raw HTML from text you don't trust.
  • Expecting GFM tables in CommonMark core mode.
  • Linking to a stylesheet on a CDN in the downloaded page.

Tips

  • Runs entirely in your browser. Your input is not uploaded or stored.

Frequently asked questions

How complete is it?

It covers common CommonMark and GFM syntax. It is built in-house rather than a full reference parser, so very unusual edge cases can differ.

Privacy?

Runs entirely in your browser. Your input is not uploaded or stored.

Related tools

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Cite this tool

Zerdly. (2026). Markdown to HTML Converter. Retrieved from https://www.zerdly.com/tools/markdown-to-html-converter/

Tip: Enter any known values to calculate the remaining results.

Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.