Markdown viewer and editor with live preview.

Markdown is a plain-text format for writing structured documents, created by John Gruber in 2004. You mark structure with ordinary characters: # for headings, - or * for lists, **double asterisks** for bold, backticks for code, and square brackets followed by parentheses for links. It reads naturally as text and converts cleanly to HTML, which is why READMEs, documentation sites, wikis, issue trackers, note apps, chat tools and AI assistants all use it.

Because a Markdown file is just text, it works with version control, diffs cleanly, stays readable without any special software and moves easily between tools. Static site generators and headless CMS platforms often store content as Markdown for exactly these reasons.

Markdown is also the default output format of most AI assistants built on large language models. Pasting an AI-generated answer here is a quick way to read its tables and code properly, check its structure, or turn it into HTML for a page or an email.

A .md file is plain text, so any text editor can open it, but you will see the raw syntax rather than the formatted document. To read it formatted, press Open .md above or drag the file onto the editor; it is rendered immediately, with a table of contents for its headings. Files of up to 2 MB with .md, .markdown, .mdown or .txt extensions are supported.

The file is read by your browser and never uploaded, which makes the viewer safe for internal documentation, meeting notes and drafts. Edit it in place, then save it back as .md or export it as HTML.

The original Markdown description left many cases ambiguous, so different tools rendered the same file differently. CommonMark, first released in 2014, is a precise specification of core Markdown with hundreds of examples: headings, emphasis, links, images, lists, block quotes and code. GitHub Flavored Markdown (GFM) is GitHub's formal superset of CommonMark. It adds tables with column alignment, task lists, strikethrough and automatic links for bare URLs and www. addresses.

This viewer implements the CommonMark essentials plus those GFM extensions, so a README previews here much as it will on GitHub or GitLab. GitHub also renders features that are outside the GFM specification, such as footnotes, alert callouts, Mermaid diagrams and maths; those appear here as plain text.

Headings in both styles (# Heading, or a line underlined with === or ---), paragraphs, emphasis with * or _, strong text, strikethrough with ~~, inline code, links and images with optional titles, block quotes, nested bulleted and numbered lists, task lists with [ ] and [x], horizontal rules, tables with left, centre and right alignment, fenced code blocks with ``` or ~~~ and a language label, indented code blocks, and hard line breaks with two trailing spaces or a backslash. Backslash escapes such as \* show a literal character.

Code blocks get light, language-agnostic syntax colouring for comments, strings, numbers and keywords. Headings get stable anchor IDs and appear in the Contents menu, and the status bar shows the word count, character count and an estimated reading time. Reference-style links, raw HTML and HTML entities such as © are not rendered.

Copy HTML puts clean, escaped HTML on your clipboard, ready to paste into a CMS, an email template or a web page. The .html button downloads a standalone page with the document and simple, readable styles, which opens in any browser and can be printed to PDF from there. The .md button saves your edited Markdown, keeping the original file name.

The exported HTML contains only standard elements such as headings, paragraphs, lists, tables, code, links and images, without scripts or tracking, so it is easy to restyle with your own CSS.

Semantic HTML also helps accessibility and search. Use one top-level # heading per document, keep heading levels in order without skipping, give every image meaningful alt text, and write link text that makes sense out of context instead of 'click here'.

Markdown allows raw HTML, and a document you paste or open may come from anywhere. Rendering it would let a <script> tag, an onerror attribute or a javascript: link run code in your browser, a classic cross-site scripting attack. This viewer treats every document as untrusted: raw HTML is displayed as text, links are limited to http, https, mailto and relative URLs, and images to http, https and embedded data images.

The same rule applies when you render user-written Markdown in your own product. Use a parser that escapes HTML or a well-maintained sanitiser after rendering, and never pass user content straight to innerHTML.

Lines run together: a single line break inside a paragraph is a soft break and renders as a space. End the line with two spaces or a backslash for a line break, or leave a blank line for a new paragraph. Table not rendering: a table needs a header row followed by a delimiter row such as |---|:---:|---:|, and each row on its own line. Unexpected italics: an asterisk between characters, as in 2*3*4, starts emphasis; escape it as 2\*3\*4 or wrap the expression in backticks. Underscores inside words such as snake_case_name are left alone, as in CommonMark.

A numbered list that starts at another number, such as 3., keeps that start number. A list directly after a paragraph works when it starts with - or 1.; for other starting numbers, add a blank line first.