Markdown Viewer

Renders local and hosted Markdown files in GitHub style, with a one-click toggle between preview and source.

Markdown Viewer renders .md files as formatted documents in Chrome. Open a Markdown file — on your disk or on the web — and read it typeset instead of as a wall of plain text. ONE-TIME SETUP FOR LOCAL FILES Chrome does not give extensions access to file:// URLs by default. To read Markdown on your own disk, open chrome://extensions, click Details on Markdown Viewer, and turn on "Allow access to file URLs". Until you do, local .md files stay as plain text. WHAT YOU GET • GitHub-style rendering: headings, lists, tables, blockquotes and task lists • Syntax highlighting for fenced code blocks, with a copy button on every block • Mermaid diagrams — flowcharts, sequence diagrams and the rest • LaTeX math with KaTeX, written as $inline$ and $$display$$ • Alert boxes, in GitHub's own notation — > [!NOTE], [!TIP], [!IMPORTANT], [!WARNING], [!CAUTION] — and in the ::: tip container form • A sidebar outline that tracks your scroll position, collapses out of the way, and slides over the text on narrow windows • Heading anchors that work for non-ASCII headings too, and a [[toc]] marker if you would rather place the contents list yourself • A back-to-top button MAKE IT LOOK THE WAY YOU READ • Light, dark, or automatic — the automatic setting follows your system colour scheme • Text size, font, maximum width, and centred or left-aligned text • Wrap long code lines instead of scrolling them • Zen mode hides every control and leaves only the document • Your own custom CSS, if you want the last word • One button puts every setting back to its default MORE MARKDOWN, EACH ON A SWITCH Superscript, subscript, inserted text, highlighted text, abbreviations, definition lists, footnotes, task lists, extended (MultiMarkdown) tables, emoji, math, alert boxes, [[toc]], hiding YAML front matter, auto-linking bare URLs and smart punctuation can each be turned on or off from the toolbar popup. THE TOOLBAR POPUP Switch the current tab between preview and source, pick which of the two you get by default, change any of the settings above, and choose the interface language — automatic, English or Japanese. THE EXTENSION MAKES NO NETWORK REQUESTS Every library it uses is bundled in the extension package, the maths fonts included, so nothing is fetched while you browse and no remote code is executed. The file you open is rendered in the tab and never uploaded. Your settings are kept on your own device. There is one exception, and it is yours to make: if you write custom CSS that points at an external resource with url() or @import, your browser will fetch it, exactly as the CSS you wrote asks it to. ABOUT THE PERMISSION WARNING Chrome warns that this extension can read and change your data on all websites. That is because Markdown files can be hosted anywhere, and the extension has to read the file's text in the tab to render it. In practice it only activates on URLs ending in .md, .markdown, .mdown or .mkd. Ordinary web pages are left untouched. SUPPORTED EXTENSIONS .md, .markdown, .mdown, .mkd, in lowercase and uppercase. URLs with query strings, such as guide.md?ref=nav, are rendered too. KNOWN LIMITS • Markdown served as a download, or with no file extension, is not rendered. • Mixed-case spellings other than .md — .MarkDown, for example — are not matched. • Google Drive share links are not rendered. Their URLs carry no file extension, and the page Drive shows you is Google's own viewer rather than the file itself. Download the file and open it locally, or put it somewhere that serves the raw text. • PlantUML and Graphviz diagrams are not drawn. PlantUML renders on a remote server, which would mean sending your document off your machine — so it is left out on purpose. Mermaid covers most of the same ground and runs entirely in the tab. • There is no automatic reload. After editing a file, refresh the tab. • There are no configurable keyboard shortcuts. Esc leaves Zen mode; everything else is done from the toolbar popup.