Markdown Preview Pane

WHAT IT DOES

Markdown Preview Pane is a browser extension that detects textareas containing Markdown content on any webpage and displays a live preview pane showing the rendered HTML. As you type in the textarea, the preview updates in real-time, showing how your Markdown will look when rendered. It supports all common Markdown syntax: headers (H1-H6), bold and italic text, ordered and unordered lists, code blocks and inline code, links, images, blockquotes, and horizontal rules. The preview pane appears automatically when you focus a Markdown textarea, and you can toggle it on and off with a single click. The tool is ideal for writers, developers, content creators, students, and anyone who writes Markdown in web-based editors, comment fields, or documentation pages.

WHERE IT RUNS

Markdown Preview Pane works on any webpage that contains textareas. It runs locally in your browser as a lightweight userscript, scanning textareas for Markdown indicators such as the presence of headers (#), bold/italic markers (*), code blocks (```), or the words "markdown" or "md" in the textarea's ID, name, class, or placeholder. It works on content management systems, code editors, documentation platforms, blogging interfaces, forum comment fields, and any other page where Markdown is used. The tool handles static pages, dynamically loaded content via AJAX, and single-page applications where textareas appear and disappear without page reloads. All processing occurs entirely in your browser—no text is ever sent to any server.

HOW TO USE

After installation, open the floating panel by clicking the extension icon. The panel includes a toggle to show or hide the preview pane and a button to scan for textareas. To use the tool, simply focus any textarea that contains Markdown content—the preview pane will appear to the right of the textarea, showing a live rendered HTML preview. As you type, the preview updates instantly with proper formatting: headers appear in different sizes, bold and italic text are styled, lists are indented with bullets or numbers, code blocks are monospaced, links are clickable, and blockquotes are indented with a colored border. Use the "Show preview pane" toggle in the panel to hide or show the preview. Click the "Scan for textareas" button to manually trigger a rescan if new textareas appear on the page. The preview pane can be closed by clicking the ✕ button in its header or by toggling it off in the panel.

REAL MECHANISM — WHY THIS WORKS

Most Markdown preview tools require copying text to an external website, installing a separate editor, or using a browser extension with a fixed editor interface. Markdown Preview Pane uses a DOM-integrated approach that works with any existing textarea on any page. The tool first identifies candidate textareas by scanning for Markdown indicators using a combination of attribute analysis and content heuristics. Once a textarea is focused, the tool creates a floating preview pane positioned to the right of the textarea, setting the textarea's parent to position:relative to anchor the preview correctly. The preview is rendered using a custom Markdown parser that processes common Markdown syntax through a series of regex-based transformations. The parser handles headers, bold/italic, code blocks, inline code, links, images, lists, blockquotes, and horizontal rules. It also prevents XSS by escaping HTML characters before rendering. When the user types, an input event listener triggers the preview update, throttled to avoid excessive rendering. The preview pane persists while the textarea is focused and is removed when another textarea is focused or when the page changes. This approach ensures accurate, fast, and fully private Markdown preview without requiring any external services or network requests.

THE PANEL

The floating panel is fully draggable and remembers its position per site, snapping to the edges of the viewport when dragged near them. You can collapse the panel to a small icon to minimize screen distraction and expand it back with a single click. The panel is resizable from the bottom-right corner, giving you more space to view controls. Press the Escape key to close the panel instantly. The panel remains open across page navigation within the same domain, maintaining your current toggle states. All preferences—panel position and preview visibility state—are saved per domain for a seamless experience.

PLEASE NOTE

Markdown Preview Pane requires the free BotGentz extension to be installed and enabled, as it relies on the cross-extension messaging API provided by BotGentz for DOM access permissions. Because websites frequently update their structure, textarea detection and preview rendering may require periodic script updates to maintain compatibility with specific sites. If the tool does not detect a textarea or show a preview as expected, please check for updates or report the issue. All text processing occurs entirely in your browser. No Markdown content, rendered HTML, or usage data are ever sent to any server. The extension does not read, store, or transmit any personal information. It only reads the DOM to detect textareas and reads textarea values to render previews at your explicit request.