Half the architecture sketches on the internet trace back to Excalidraw - the MIT-licensed virtual whiteboard whose hand-drawn aesthetic made technical diagramming feel approachable, at roughly 85,000 GitHub stars. The infinite canvas offers rectangles, ellipses, diamonds, arrows with smart binding and labels, free-draw, text, images, and an eraser, with full undo/redo, zoom, dark mode, and keyboard-first ergonomics. Community shape libraries add thousands of pre-built elements - AWS architecture icons, flowchart stencils, UI wireframe kits - and everything exports to PNG, SVG, the clipboard, or the open .excalidraw JSON format that keeps drawings diffable and portable. Live collaboration works on a share-a-link model with live cursors and a laser pointer for presenting, and it is end-to-end encrypted by design: the room key travels in the URL hash, which never reaches the server, so the WebSocket relay only ever sees ciphertext. The architecture is remarkably light - the app is a static bundle served by Nginx, drawings persist locally in the browser, and the stateless excalidraw-room relay handles multiplayer - so a self-hosted deployment gives unlimited boards and collaborators with near-zero resource cost, replacing per-editor whiteboard subscriptions.

The drawing surface inside WebRTC conference tools like Meetzi and the LAMS online-learning platform is Whiteboard (by cracker0dks) - a lightweight Node.js collaborative sketchboard built to be embedded and customized, which also slots into Nextcloud via the External Sites app. Everyone opening the same whiteboardid URL parameter draws on the same board, with remote user cursors visible live, per-user undo/redo, and an indicator showing the smallest participating screen so nobody draws outside a colleague's view. Content handling goes beyond pen strokes: drag-and-drop or paste images and PDFs from any PC or browser, then resize, rotate, and draw over them on canvas or background; add text and sticky notes; hold Shift for angle-snapped lines and perfect squares. Every function has a keybinding - deliberately friendly to pen displays like Wacom and XP-Pen whose hardware buttons map to shortcuts. Boards save to image or JSON (with reload), export directly to Nextcloud via WebDAV, and persist across restarts with the file-database option. A REST API with bundled interactive docs allows full programmatic control, an optional access token locks down uploads, and YAML configuration tunes behavior and performance. MIT-licensed and reverse-proxy friendly.

A Node.js server, a large shared canvas, and a URL - WBO (Whiteboard Ophir) is collaborative whiteboarding reduced to its essence. There are no accounts and no setup - to collaborate, you send someone the board's link, and every stroke appears for all connected users in real time over WebSockets, with cursor positions shared so you can see where collaborators are working. Board state persists automatically and continuously, so a diagram drawn in today's lesson is still there next week at the same URL. Boards come in three flavors: a public free-for-all, private boards with random unguessable names, and named boards with custom URLs shared by anyone who knows the name. The tools cover teaching and brainstorming needs - pencil, straight lines, rectangles, ellipses, text annotations, eraser, a full color palette with brush sizes - and boards export as SVG or PNG. Despite the simplicity, the server is production-minded: JWT authentication gates board access with granular capabilities (open, edit, and clear as separate permissions), rate limiting caps per-client message volume, reverse-proxy and subpath deployment are supported, and OpenTelemetry provides metrics, logs, and traces. It works on tablets and touch devices, speaks multiple languages, and consumes minimal resources. AGPL-licensed.

ExcaliDash adds persistent storage, access control, version history, and real-time collaboration to Excalidraw, transforming ephemeral whiteboarding sessions into a managed drawing library your team can rely on. The Node.js/Express backend with React/TypeScript frontend deploys via Docker Compose on port 6767, using Prisma ORM on SQLite for all drawings, users, and metadata. WebSocket-powered collaboration lets multiple users edit the same canvas simultaneously with live cursor presence. Drawing snapshots preserve every revision with visual preview and one-click restore to any previous state. Three authentication modes handle different deployment needs: local email/password for personal use, hybrid mode mixing native credentials with OIDC for gradual enterprise adoption, and enforced OIDC-only for organizations requiring SSO through providers like Authentik or Keycloak. Scoped sharing controls determine whether drawings stay private, shared internally with team members, or accessible via external links without authentication. Collections organize drawings through drag-and-drop grouping, full-text search locates any diagram instantly, and exports use the non-proprietary .excalidraw format ensuring complete data portability. 1,350+ stars since November 2025. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

Gaining over 71,000 GitHub stars as one of the fastest-rising knowledge management platforms, AFFiNE merges the document editing capabilities of Notion, the infinite canvas of Miro, and the structured data of Airtable into a single cohesive workspace. The block-based editor built on the custom BlockSuite framework supports rich text, code blocks, embeds, tables, kanban boards, and database views with drag-and-drop composition. The whiteboard mode provides an infinite canvas where users can freely mix documents, sticky notes, shapes, connectors, and hand-drawn elements, enabling visual thinking alongside structured note-taking. Real-time collaboration allows multiple users to edit documents and whiteboards simultaneously with cursor presence, comment threads, and version history. The local-first architecture stores all data on your device by default using CRDT-based synchronization, ensuring offline access and data sovereignty, with optional cloud sync for cross-device availability. Workspaces organize content into hierarchical page trees with full-text search, favorites, tags, and trash management. The platform supports Markdown import and export, PDF export, and HTML export for interoperability. AI features powered by configurable LLM providers enable writing assistance, summarization, translation, and content generation directly within documents. The theming system supports light and dark modes with customizable accent colors. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Licensed under MIT with an open-source self-hosted edition.

Technical teams frequently struggle to keep software architecture diagrams synchronized with evolving codebases and documentation repositories. Atlantis Diagrams delivers a unified self-hosted workspace that couples code-driven Mermaid.js diagramming with structured Markdown knowledge bases in a responsive web interface. Engineers can compose flowcharts, sequence diagrams, state machines, entity-relationship models, and Gantt schedules using split-view CodeMirror editors with real-time SVG rendering. An integrated version history tracker automatically captures revision checkpoints across the last 15 document states, letting authors compare modifications and restore previous iterations without data loss. The linked notes environment supports rich Markdown editing, LaTeX mathematical formulas, interactive task checklists, tag indexing, and full-text keyword searches across personal documentation libraries. Canvas controls allow users to pan, zoom, inspect individual nodes, and export finalized graphics directly into vector SVG, high-resolution PNG, or printable PDF documents. Storage engines adapt to deployment scale, running on zero-configuration SQLite databases out of the box with optional PostgreSQL, MySQL, and Redis caching layers for high-concurrency environments. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Open-source alternative to OpenAI's Canvas — a collaborative writing and coding environment where AI agents help you draft, edit, and refine documents through an agentic architecture built on LangGraph. The dual-mode editor combines a BlockNote rich text editor for live-rendered markdown with a CodeMirror-based code editor supporting syntax highlighting across multiple programming languages, letting you switch between prose and code artifacts within the same session. The built-in reflection agent automatically generates style rules and user insights from your chat history, storing them in a shared LangGraph memory store that persists across sessions for increasingly personalized assistance. Pre-built quick actions provide one-click access to common writing transformations including summarize, expand, simplify, and translate, while coding actions offer explain, refactor, add comments, and convert between languages. The monorepo architecture separates the Next.js 14 frontend from the LangGraph agent backend, connecting via HTTP and WebSocket protocols through the @langchain/langgraph-sdk client. Seven LLM providers are supported out of the box — OpenAI, Anthropic Claude, Google Gemini, Fireworks AI, Groq, Azure OpenAI, and local Ollama models — with Supabase handling authentication and data persistence. Deploy via Docker or build from source. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

In continuous open-source development since 2009, Etherpad is the original really-real-time collaborative editor - used by Wikimedia, governments, EU public-sector institutions, and tens of thousands of self-hosters. Its core idea is visible authorship: every keystroke is attributed with author colors, every revision preserved, and the timeslider lets you scrub through a document's entire history character by character. Multiple people type into the same pad and see each other's changes instantly - it scales to thousands of simultaneous editors per pad. The base install is deliberately lightweight; capability comes from roughly 290 plugins installable from the admin web UI: comments, images, tables, drawing, video chat via WebRTC, math rendering, code highlighting, and authentication via OAuth, LDAP, or OpenID. AI is pointedly a plugin, not a default - you choose the model and infrastructure, or never turn it on. There is no telemetry. For integrators, an HTTP API (with OpenAPI definitions at /api/openapi.json) manages pads, users, and groups for embedding in your own applications, and the ueberDB abstraction layer supports PostgreSQL, MySQL, Redis, MongoDB, and SQLite backends. Full data export is built in, the format is open, it is translated into 105 languages, and it runs on anything from a Raspberry Pi to a server farm. Apache 2.0 licensed, Node.js based.

Real-time collaborative Markdown behind your own firewall: HedgeDoc (formerly CodiMD, descended from HackMD's open-source edition) keeps team notes on team infrastructure. Share a note's URL and collaborators are editing together instantly - live cursors, changes appearing keystroke by keystroke - in a three-mode interface that toggles between raw Markdown, rendered preview, and side-by-side split. The Markdown dialect is extended where engineers need it: Mermaid, Graphviz, and Vega-Lite diagrams, MathJax for equations, syntax-highlighted code blocks, embedded content, and a presentation mode that turns a note into reveal.js slides with a single YAML header. A dropdown permission system controls each note - freely editable, limited to signed-in users, or locked read-only - and published notes become clean read-only pages for wider distribution. Revisions track every change with the ability to revert to any earlier version. The AGPL-3.0 codebase is light enough to run on a Raspberry Pi and deploys via Docker with PostgreSQL, MySQL, or SQLite. Authentication covers LDAP, SAML, OAuth2, and email. It deliberately stays a focused document editor - no page trees or kanban - and does that one job with excellent keyboard-first ergonomics for meeting notes, RFCs, runbooks, and shared scratchpads.

Upload a report, ask a "what if" question in plain language, and MiroFish builds a small simulated society that plays out the answer before you commit to a decision. It reads your seed documents, whether news, policy drafts, financial signals, or a novel, and extracts entities and relationships into a GraphRAG knowledge graph. Entities from the graph become agents with a profession, a biography, and interest tags, and the app estimates simulation rounds from the simulated time span, with a custom mode for shorter runs. Agents post and react on two simulated platforms at once, a feed-style plaza and a topic community, while a live monitor tracks rounds, elapsed simulated time, and actions. A ReportAgent then plans an outline and writes the prediction report section by section with the InsightForge, PanoramaSearch, QuickSearch, and InterviewSubAgent tools. Afterward you can keep questioning the ReportAgent, chat with any individual agent, or send a survey question to a selected group and read their answers. Typical uses include rehearsing public relations responses, testing policy drafts against likely reactions, and exploring alternate endings for a story. The interface switches between English and Chinese, and you bring your own model: any OpenAI SDK compatible LLM endpoint works, Zep Cloud stores agent memory, and the project suggests starting under 40 rounds because runs consume many tokens. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

Schema design with no account and a few clicks: drawDB is the browser-based entity-relationship diagram editor and SQL generator - an AGPL-3.0 React project with over 37,000 GitHub stars. Draw tables with columns, data types, defaults, and constraints; connect fields to create foreign-key relationships; group tables into labeled subject areas; and annotate with notes. When the design is ready, one export produces CREATE TABLE DDL - with constraints, indexes, and foreign keys - targeted at MySQL, PostgreSQL, SQLite, MariaDB, SQL Server, or Oracle. Diagrams can be database-specific, unlocking every native type plus dialect features like PostgreSQL enums and composite custom types, or generic for portability across all supported flavors. The reverse direction works too: paste existing DDL into the import dialog and drawDB renders your live schema as a navigable diagram - the fastest way to document an inherited database. Versioning and migration-script generation track schema evolution, full editor ergonomics (undo/redo, copy/paste, duplicate, themes) keep iteration fast, and diagrams export as PNG, SVG, or shareable JSON. Everything runs client-side against browser storage - no backend database connection needed - so the self-hosted Docker deployment is a featherweight static app that keeps proprietary schema designs entirely on your infrastructure.

Most design tools stop at prototyping; Quant-UX also measures how real users actually perform with the prototype. The visual editor creates prototypes that behave like real apps - functional input widgets, animations, form validation, data binding across screens, and business logic modeled with REST requests and decision elements. Design systems are first-class, with components, design tokens, and master screens; if you design elsewhere, drop in image files or import from Figma. Testing is a shared link or QR code - no installs on the tester's side. Define user tasks up front, and Quant-UX records every session: click heatmaps show where users found (or missed) actionable elements, user journey graphs expose lost users, drop-off charts reveal where tasks stall, and success rates and task KPIs are extracted automatically into a dashboard. An A/B test operator wires two design variants into one prototype and compares task duration, success rate, and interaction counts. In-prototype surveys collect qualitative feedback alongside the numbers, and an AI assistant generates prototype fragments like styled forms on request. The RepoCloud deployment runs the full stack - frontend, backend, and WebSocket server containers over MongoDB - so all test recordings and research data stay on your infrastructure.