Markdown Editor

Why Use an Online Markdown Editor?

Markdown is the default writing format for software documentation, README files, technical blogs, and knowledge bases. According to GitHub's 2024 Octoverse report, over 420 million repositories host at least one Markdown file, and the format has expanded far beyond developer circles - content teams, technical writers, and educators now write in Markdown daily. Despite this ubiquity, most desktop Markdown editors require installation, account creation, or a paid subscription. A browser-based editor removes every barrier: open the page, start writing.

Privacy-conscious writers increasingly question whether their drafts are being stored in the cloud. This editor processes everything locally - the marked parser runs in your JavaScript engine, the preview renders in your DOM, and document titles, text, and saved versions are stored in this browser’s IndexedDB, with localStorage as a fallback. Use Delete all local notes to remove both writing tools’ documents, versions, and old draft. No account, no cloud sync, no analytics that capture content.

How Does Live Markdown Preview Work?

As you type, a debounced listener passes your Markdown source to marked v17, a high-performance GFM parser written in JavaScript. Marked converts the Markdown AST into raw HTML in under 5 milliseconds for typical documents. That HTML is then sanitized by DOMPurify - which strips any injected <script> tags, event handlers, or javascript: URIs - before being injected into the preview pane as innerHTML.

The two-panel split layout mirrors the workflow professional tools like GitHub's own web editor and VS Code's Markdown preview use. On desktop, both panels are visible simultaneously. On mobile, a tab switcher toggles between the Write and Preview views to preserve screen space. The preview re-renders within 400 milliseconds of your last keystroke, giving you near-instant feedback without blocking the editor while you type.

Which Markdown Editing Features Does brownie.tools Provide?

Choose an editor that fits your workflow: preview support, export formats, installation requirements, and draft storage all matter. This editor offers the following features in your browser.

Feature	brownie.tools
GFM support	Tables, task lists, and strikethrough
Processing	In your browser
Installation	No installation required
Account	No account required
HTML export	Copy or download
Local documents	Create, rename, delete, switch, and back up documents as JSON
Version history	Save snapshots, preview, and restore up to 30 versions per document; 20 MB total with oldest-first eviction

What Is GitHub Flavored Markdown?

GitHub Flavored Markdown (GFM) is a strict superset of CommonMark, the standardized Markdown specification published in 2016. GitHub introduced GFM to add features that software documentation requires but plain Markdown lacks: fenced code blocks with language identifiers (enabling syntax highlighting), tables, task lists using - [ ] and - [x] syntax, strikethrough with ~~double tildes~~, and autolinked URLs. In 2017 GitHub formalized the GFM specification at github.github.com/gfm , and it has since been adopted by GitLab, Gitea, Jira, Notion, and dozens of other platforms.

The practical difference between GFM and standard Markdown matters when you share documents across tools. A table written as GFM renders correctly on GitHub, in VS Code's preview, and in this editor - but may appear as plain text in tools that only implement the original 2004 John Gruber Markdown specification. Writing in GFM-compliant Markdown ensures maximum portability.

Who Benefits From a Browser-Based Markdown Editor?

Developers use Markdown daily for README files, pull request descriptions, inline documentation, and CHANGELOG entries. A quick browser tab is faster than opening a full IDE when you need to draft a single document or prototype formatting before committing.

Technical writers working on API documentation, developer portals, or internal wikis benefit from the live split preview: what you see on the right is exactly what your readers will see, without a separate build step. The HTML export produces clean, semantic markup that integrates directly into documentation pipelines.

Students and researchers write lab reports, lecture notes, and thesis outlines in Markdown to avoid formatting lock-in. Text files in Markdown are future-proof - they remain readable in any text editor without special software, unlike .docx or proprietary note formats. A 2023 survey by Stack Overflow found that 49% of developers use Markdown as their primary documentation format, up from 35% in 2019.

Bloggers and content creators on platforms like Ghost, Hugo, or Jekyll write posts in Markdown. This editor provides a clean, distraction-free environment to draft content and verify formatting before pasting into a CMS. The HTML export button delivers publish-ready markup in a single click.

For any writing task where plain text formatting, portability, and privacy matter, a browser- based Markdown editor with live preview is the most efficient tool available - no installation, no account, no data leaving your device.

How Does This Markdown Editor Keep Your Drafts Private?

Cloud-synced editors send drafts to remote services for storage or collaboration. This editor makes zero uploads: parsing, math, diagrams and syntax highlighting all run in your browser, and document titles, text, and saved versions are stored in this browser’s IndexedDB, with localStorage as a fallback. Use Delete all local notes to remove both writing tools’ documents, versions, and old draft, or clear this site’s browser data. Downloaded backups must be deleted separately. You can verify this yourself by opening the Network tab in your browser's developer tools while you type, add a Mermaid diagram or insert a formula. The diagram and math libraries are served from this site and load on demand, and no document content is sent with those requests.

How Do You Add Diagrams, Math, and Code Highlighting?

Fenced blocks labelled mermaid become SVG diagrams, $...$ and $$...$$ become KaTeX math, and fenced blocks with a supported language label are highlighted. Diagram output is sanitized before it is inserted into the preview, and Mermaid runs in its strict security mode, so a script placed in a diagram label does not execute. Everything is included in the HTML export and in the print dialog output.