We built an open‑source, in‑browser Markdown editor—fast

Meet Markdown Web: a polished, open‑source Markdown editor that runs entirely in your browser, ships with a full AI toolkit (OpenAI + Anthropic), first‑class Git workflows, beautiful themes, export/print you can rely on, and a mobile‑ready UX. It’s the tool we wanted for everyday writing, docs, and technical notes—so we built it.

And with help from OpenAI’s Codex CLI, we moved from scaffolding to a production‑ready app in practically no time. Codex‑assisted generation let us stand up endpoints, components, and whole workflows quickly, while we focused on architecture, UX, and hardening.

Try it and star the repo: https://github.com/vultuk/markdown-web

Highlights at a glance

In‑browser editor with live preview and split‑view
AI built in: OpenAI + Anthropic, selection‑based edits, Q&A mode, model selection
Precise cost tracking with per‑file usage logs and unified response formats
Git integration: status, badges, add/stage, commit, push, clone, and context menus
Always‑on Mermaid diagrams, syntax highlighting, and professional themes
Export to PDF/Markdown with print‑perfect styling
PWA install, mobile responsiveness, and accessibility
Secure by default: password auth, session cookies, and safe key storage
Settings that stick: layout, sidebar behavior, theme, AI provider/model, keys

AI that respects your workflow (and your wallet)

We’ve built a multi‑provider AI layer that feels native to the editor:

OpenAI + Anthropic support with unified architecture and provider‑aware operations
Dual‑mode AI: Adjust (modify content) or Ask (Q&A over your markdown)
Selection‑based edits: target a paragraph, code block, or section—without touching the rest
Model selection with smart aliasing/migration for seamless upgrades
Accurate cost tracking across providers with:
Per‑operation cost + token usage returned from every AI endpoint
Per‑file log files with path‑based organization
Status bar with cumulative cost visibility
Consistent response parsing and robust sanitization
Keys stored securely in local settings (with environment fallback)

Latest releases expanded pricing coverage, added path context to AI responses, and unified response formats so you get trustworthy numbers and cleaner analytics. Anthropic models (Claude Sonnet/Opus) and OpenAI models are both first‑class citizens.

Git, but friendly

You shouldn’t have to leave your editor to do the basics—or even most of the advanced stuff:

Repository detection with smart Git badges on folders
Real‑time file/repo status indicators (untracked, modified, deleted)
Context menus (desktop right‑click, mobile double‑tap) for:
Add/Stage, Commit (with modal), Push
Clone repo into any directory
Deleted file handling that “just works” (including git rm --cached)
Detailed command feedback and strong error handling

From status to push, everything lives where you expect it: in the file explorer and context menus, with clean, VS Code‑inspired UI.

An editor you’ll actually enjoy

Split‑view preview with draggable resizer and 50/50 double‑click reset
Syntax highlighting with automatic light/dark themes
Always‑on Mermaid diagrams with local‑first loading and CDN fallback
Visual selection highlighting when AI modal is open
Drag‑and‑drop file/folder moves with auto‑expand on hover
Toast notifications and clear error reporting
Mobile‑aware interactions and keyboard accessibility

Export and print you can trust

One‑click PDF export and Markdown download
Print output that mirrors your theme with professional typography
Clean, multipage flow (no clipped boxes), smart page breaks, and link handling

Secure by default

Password authentication (enabled by default) with session cookies
Scrypt hashing, HMAC session signing, CSRF protections, and rate limiting
API credentials sent with proper cookie handling across all endpoints
AI keys stored locally in settings with masked input and validation

Settings that get out of your way

Centralized settings modal for preview layout (full vs split), sidebar behavior (overlay vs inline), theme, AI provider/model, and API keys
Preferences persist across sessions and devices
Sensible defaults for desktop and mobile

Built at startup speed with OpenAI’s Codex CLI

Codex CLI accelerated our build dramatically: - Rapid scaffolding of endpoints, components, and interfaces - Iterative UX polishing with human‑in‑the‑loop refinement - Faster hardening passes (error handling, validation, and logging) - More time for product thinking, less time on boilerplate

The result: a high‑quality app shipped quickly—with a roadmap that keeps compounding.

Under the hood (for developers)

TypeScript end‑to‑end, clean provider abstractions, and shared interfaces
AI endpoints:
/api/ai/status for capability detection
/api/ai/apply for content modification (selection‑aware)
/api/ai/ask for Q&A without altering content
/api/ai/cost for per‑file summaries
Git endpoints for add, commit, push, clone, and status
Theming system with print/export integration
PWA registration and offline‑friendly caching
Robust path validation and safe file operations
JSON_LIMIT env support (50 MB default) for large docs

What’s new

Recent releases focused on: - Multi‑provider AI with Anthropic support and pricing/cost parity - Accurate, unified cost tracking returned from every AI operation - Model aliasing and smooth migrations across naming changes - File‑path context in AI logs for cleaner analytics - Full Git workflow (status, stage/add, commit, push, clone) with context menus - Always‑on Mermaid with smarter loading for reliability - Drag‑and‑drop file management and mobile‑first interactions - Password auth by default, with better route ordering and cookie handling - Professional SVG icon system, accessibility improvements, and responsive polish

The full changelog is available in the repo if you want to dive deep.

Call for contributors

We’re building in the open and would love your help: - Star the project, file issues, and propose features - Contribute themes, integrations, and UX improvements - Share your workflows and ideas for the AI + Git experience

Start here: https://github.com/vultuk/markdown-web

If you write, document, code, or just love clean tools, we think you’ll feel right at home.