With over 75,000 GitHub stars and native apps across macOS, Windows, Linux, iOS, and Android, AppFlowy is the most widely adopted open-source alternative to Notion — delivering the same block-based workspace model with full data sovereignty. The Flutter frontend renders natively on every platform while a Rust backend powered by Actix-web and Tokio handles CRDT-based real-time collaboration, ensuring sub-second sync across devices with conflict-free concurrent editing. Relational databases support grid, board, kanban, calendar, and gallery views over the same dataset, with two-way relations, rollups, advanced filters, sorts, and formula calculations that cover the majority of Notion's database workflows. The block editor supports 40+ content types including nested pages, toggles, callouts, code blocks with syntax highlighting, embeds, and slash-command insertion. AI integration connects to OpenAI, Anthropic, or local models via Ollama for writing assistance, summarization, and translation — all without sending data off-premises when using on-prem LLMs. Team spaces with workspace-level and per-page permissions, OAuth and SSO authentication through GoTrue, and S3-compatible object storage via MinIO provide enterprise-grade access control and file management. The self-hosted stack deploys through Docker Compose with PostgreSQL for metadata, Redis for caching and pub/sub, and a dedicated background worker for imports and email notifications. Offline-first architecture ensures the desktop app functions without connectivity, syncing changes when the connection resumes. 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.

An open-source alternative to Notion and Google Docs developed jointly by France's DINUM and Germany's ZenDiS that prioritizes data sovereignty, real-time collaboration, and structured knowledge management. The Yjs-powered CRDT engine provides live cursors, presence indicators, and inline comments enabling teams to edit simultaneously without conflicts, while BlockNote.js renders a clean block-based editing experience with rich text formatting, Markdown shortcuts, and drag-and-drop content organization. Hierarchical sub-documents create wiki-style knowledge bases where documentation nests naturally into navigable structures, and a dedicated slide mode transforms any document into a presentation without separate tooling. The document API separates content from metadata with distinct endpoints for formatted content, raw content streams, and document properties. Optional AI integration connects to configurable language models for writing assistance, summarization, and content generation directly within the editor. Access control supports granular permissions per document with team sharing, public links, and invitation flows. DOCX import brings existing documents into the platform while maintaining formatting fidelity. The Django backend serves a REST API with PostgreSQL storage, Redis caching, and S3-compatible media handling. Deploy via Docker Compose, Kubernetes with the official Helm chart, Nix, or YunoHost on your own infrastructure. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Matrix's flagship client, built by the protocol's creators: Element brings the decentralized open standard for real-time communication to web, desktop, iOS, and Android. Paired with a Matrix homeserver, it delivers Slack-quality team messaging where you own every message, file, encryption key, and byte of metadata. End-to-end encryption is on by default, built on Olm and Megolm - the Double Ratchet algorithm family Signal popularized, extended for large-room scalability and publicly audited by NCC Group. Messages encrypt per-device with cross-signed device verification, so even a compromised server yields nothing readable. Federation is the defining capability: like email, users on different homeservers converse seamlessly, and 30+ bridges connect Matrix rooms to Slack, Discord, WhatsApp, and Telegram, so moving to sovereign infrastructure doesn't sever contact with anyone. Rooms support threads, reactions, file sharing, and voice and video calls via Element Call. The result is digital sovereignty chosen by governments and enterprises across Europe: your data sits on your server in your jurisdiction, portable to any other Matrix host because the protocol is an open standard. Apache-2.0 licensed, with no per-user fees at any scale.

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.

The Bitwarden server, reimplemented in Rust: Vaultwarden (formerly bitwarden_rs) is the unofficial lightweight edition. It speaks the same wire protocol as the official server, so every official Bitwarden client - browser extensions, iOS, Android, desktop, and the bw CLI - connects without modification, while the server itself runs as a single container against SQLite (or MySQL/MariaDB/PostgreSQL) instead of the official multi-container stack that wants gigabytes of RAM. Features Bitwarden gates behind paid tiers ship free: organizations with collections, groups, member roles, and policies; TOTP code storage; file attachments; Bitwarden Send; Emergency Access; event logs; and admin password reset. Two-factor options cover authenticator apps, email, FIDO2 WebAuthn, YubiKey, and Duo, and OIDC-based SSO landed natively in v1.35.0. Zero-knowledge encryption is unchanged - vault data is encrypted client-side and the master password never reaches the server. Attachments and Sends store on local disk or S3-compatible backends, an admin panel manages users and server settings, and backup is copying one data directory. Suited to individuals and teams up to roughly 50 users.

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.

SOGo adds shared calendars, address books, and a modern webmail interface to your existing Dovecot, Postfix, or Cyrus mail setup, turning familiar infrastructure into a full Exchange competitor. Rather than replacing your IMAP and SMTP servers, SOGo layers collaboration on top of them, becoming the missing link between raw mail delivery and what users actually expect from a workplace communication platform. The ActiveSync implementation synchronizes email, contacts, calendars, and tasks natively with iPhones, Android devices, and Windows without requiring users to manually configure CalDAV endpoints. CalDAV and CardDAV compliance ensures Apple Calendar, Thunderbird (via the official SOGo Connector extension), GNOME Evolution, and Android via DAVx5 all connect without plugins or workarounds. The web interface uses AngularJS Material design with responsive layouts, offering folder management, drag-and-drop calendar scheduling, contact groups, resource booking, and delegation. Shared calendars support free-busy lookups, iMIP event invitations, and per-user ACL permissions for fine-grained access across organizational units. Built on Objective-C with the GNUstep foundation, SOGo delivers exceptional performance: hundreds of concurrent ActiveSync connections from mobile devices alongside webmail and calendar traffic with sub-second response times. With 2,095+ stars and 116 releases, the project has proven its stability in production environments supporting thousands of users. The Docker deployment runs alongside PostgreSQL and memcached.

Livebook is an interactive notebook for Elixir where you write code alongside rich Markdown prose, execute it cell by cell with reactive dependency tracking, and deploy finished notebooks as standalone web applications with a single click. Nearly 6,000 GitHub stars reflect the Elixir core team's investment in a platform where code cells run on demand alongside Mermaid diagrams and KaTeX mathematical formulas. The Kino visualization library renders Vega-Lite charts, interactive data tables with sorting and pagination, Leaflet maps, and Mermaid diagrams directly within notebook output cells, while custom Kino components enable building interactive controls with sliders, text inputs, and buttons that feed values back into running code. Smart cells abstract high-level tasks into configurable UI widgets: query PostgreSQL, MySQL, SQLite, and BigQuery databases, train machine learning models with Axon, plot charts, and build map visualizations without writing boilerplate code. Real-time collaboration lets multiple users edit the same notebook simultaneously with cursor presence indicators and synchronized cell evaluation. Notebooks are stored as .livemd files, a Markdown-compatible format that renders cleanly on GitHub and integrates with standard version control workflows. Custom runtimes connect Livebook to existing Elixir applications for live introspection and documentation of running systems. The Docker image at ghcr.io/livebook-dev/livebook exposes ports 8080 and 8081 with password or token authentication. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache 2.0 licensed.

Reaching 45,000 GitHub stars within seven months of launch, Multica is the fastest-growing open-source platform for managing AI coding agents as first-class teammates — assign an issue to Claude Code, Codex, Cursor, Copilot, Kimi, or any of 21 supported agent CLIs and it picks up the work, comments progress in real time via WebSocket, raises blockers, and hands the result back for human review before anything merges. The Go backend (Chi router, sqlc-generated type-safe queries, gorilla/websocket) connects to PostgreSQL 17 with pgvector for semantic search across workspace history, while the Next.js 16 App Router frontend delivers workspace dashboards showing per-agent token spend, execution time, daily cost charts, and runtime status across unlimited connected machines. Agent Skills provide reusable methods, reference material, and supporting files that compound across runs — a persistent knowledge layer that makes each subsequent task faster and more accurate. Squads let a leader agent select the right specialist for subtasks, creating multi-agent workflows without manual orchestration. Review gates ensure no AI-generated code ships to main without explicit human approval. Self-host via Docker Compose or Kubernetes with full Git integration across GitHub, GitLab, Gitea, and Forgejo including self-hosted instances. The CLI and REST API make every surface scriptable, and Autopilot automations trigger agent runs from events. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache 2.0 licensed with additional conditions.

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.

Seatsurfing brings desk booking, room reservations, and parking management to interactive floor plans across multiple office locations, solving the coordination headache of hybrid work. The Go backend serves two React/TypeScript frontends through a single Docker container on port 8080: a Booking UI built as an installable Progressive Web App for mobile and desktop reservations, and an Admin UI for floor plan configuration, capacity enforcement, and analytics. Interactive floor plans accept uploaded office layouts where administrators visually place bookable spaces with per-space metadata and availability rules. Multi-location support handles organizations with distributed offices across multiple buildings and cities. The buddy system displays which colleagues have bookings on a given day, enabling team coordination without manual communication. Capacity management enforces occupancy limits per area with automatic denial when thresholds are reached. SSO integration supports OIDC and OAuth2 providers including Microsoft Azure AD, Keycloak, and Authentik for enterprise identity federation. Microsoft Teams and Confluence integrations embed booking directly into collaboration tools employees already use daily. The REST API enables automation and custom integrations, while the analytics dashboard tracks utilization rates, peak hours, and booking patterns. Docker Compose deployment requires only a PostgreSQL database with multi-architecture images supporting amd64 and arm64. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. GPL-3.0 licensed.

Stalwart replaces the traditional Postfix + Dovecot + SpamAssassin + calendar-server stack with one Rust binary that speaks every standard mail and collaboration protocol natively. JMAP, IMAP4rev2, POP3, SMTP, CalDAV, CardDAV, and WebDAV all run inside the same process — no glue scripts, no sidecar daemons, no version conflicts between components. The pluggable storage architecture lets operators choose RocksDB for single-node deployments, FoundationDB for distributed clusters, PostgreSQL, MySQL/MariaDB, or SQLite for the data store, S3/MinIO/Azure Blob for message blobs, and Elasticsearch or Meilisearch for full-text search, with Redis or the internal engine backing rate limiters and session state. Security features include S/MIME and OpenPGP encryption at rest, automated DKIM key generation with DNS publication, DANE and MTA-STS transport security, automatic ACME TLS provisioning, granular ACLs, rate limiting, and IP banning. The browser-based admin console manages accounts, domains, groups, mailing lists, SMTP queues, DMARC/TLS-RPT/ARF reports, and every configuration object without touching a config file, while the self-service portal at /account gives end users password reset and encryption key management. Multi-tenant support with per-tenant quotas enables hosting-platform deployments, and coordinator-less clustering via Zenoh or NATS scales horizontally by adding nodes. Deploy via Docker or the standalone binary. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL v3 licensed.

Yet Another API Development Environment delivers a self-hosted alternative to Postman designed from the ground up for teams that need secure, collaborative API development without sending sensitive credentials through third-party cloud services. The multi-user system manages team members with role-based permissions and supports external authentication through OAuth2 and OIDC providers, while all data persists in an H2 file-based database that survives container and server restarts. REST and WebSocket request testing includes environment variable substitution, request chaining, and Markdown documentation for each endpoint. The JavaScript scripting engine runs request and response scripts for automated testing and data extraction, with cron job scheduling and API-triggered execution for continuous integration workflows. Collections import directly from OpenAPI specifications and Postman exports, while outbound export generates request code in multiple languages and frameworks. The browser extension proxy for Chrome and Firefox routes requests through the user's browser to bypass CORS restrictions when testing localhost and internal APIs, with an alternative server-side proxy for headless environments. Single-file data import and export simplifies backup and migration between instances. The React and Vite frontend ships with dark mode enabled by default. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Confluence and Notion both want your team's documentation in their cloud; Docmost, an open-source collaborative wiki platform, keeps it on your server. The centerpiece is a Notion-style block editor with CRDT-based real-time collaboration: multiple people edit the same page simultaneously and changes merge without conflicts or overwrites. Content lives in spaces - per team, project, or department - with nested page trees, role-based permissions, groups, inline comments, page history with restore, and full-text search across everything. The editor covers tables, code blocks, callouts, KaTeX math, and file attachments, and diagramming is built in rather than bolted on: Mermaid, Draw.io, and Excalidraw all render inside pages, alongside embeds for Airtable, Loom, Miro, and more. Migration paths include Notion, Markdown, HTML, and ZIP archive imports (Confluence, PDF, and DOCX importers ship in the Enterprise edition, along with SSO via SAML/OIDC/LDAP and MFA). The stack is TypeScript with PostgreSQL and Redis, deploys via Docker Compose, runs in air-gapped environments with no external dependencies, and is translated into 10+ languages. The AGPL-3.0 community edition carries no per-seat fees; the project has passed 20,000 GitHub stars since its 2024 launch.

Used by the Rust language community, NASA, Dropbox, and thousands of organizations worldwide with over 25,600 GitHub stars and 1,500+ contributors, Zulip is the only modern team chat app designed from the ground up for both real-time and asynchronous communication through its unique topic-based threading model where every message belongs to a named topic within a channel. This eliminates the context collapse of linear chat by letting teams follow specific conversations without scrolling through unrelated messages, resume threads days later without losing context, and catch up on missed discussions at per-topic granularity. Server 12.0 introduced end-to-end encryption for mobile push notifications, AI-powered search ranking, channel folders for workspace organization, and expanded video conferencing with Jitsi, BigBlueButton, and Zoom integration. Over 100 native integrations connect GitHub, GitLab, Jira, Sentry, PagerDuty, Travis CI, Redmine, dbt, Nextcloud, and n8n with bidirectional notifications, while LLM-driven agents access web-public channels via a standard llms.txt interface. Full-text search covers unlimited message history across all plans, code blocks render with syntax highlighting for 250+ languages, and LaTeX math expressions display inline. The REST API with typed Python and JavaScript SDKs enables custom bots, webhook integrations, and programmatic administration. Import tools migrate entire workspaces from Slack, Microsoft Teams, Mattermost, and Rocket.Chat. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache 2.0 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.

Multiple authors can edit the same LaTeX document simultaneously in the browser with live cursor tracking, conflict-free merging, and instant PDF compilation on every save. Overleaf Community Edition brings the collaborative editing experience that millions of researchers and academics rely on, with no compile time limits, storage quotas, or collaborator caps imposed by the hosted tiers. The web editor provides syntax highlighting, auto-completion, and bracket matching alongside an integrated PDF preview panel powered by a bundled TeX Live distribution supporting pdfLaTeX, XeLaTeX, and LuaLaTeX engines. The file tree panel organizes multi-file projects with separate files for chapters, figures, bibliography references, and style definitions. BibTeX and Biber handle bibliography management, and detailed compilation logs offer clickable error navigation to the exact source line causing each issue. Users upload images, PDFs, and data files directly through the browser, and a template gallery provides starting points for journal articles, conference papers, theses, presentations, and CVs. Over 17,800 GitHub stars and a decade of active development anchor the project. The application runs as containerized microservices including the Node.js web application, MongoDB for persistence, and Redis for session management. 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.

The project that proved organizations could have Dropbox-style convenience with complete data ownership: ownCloud is the original open-source file sync and share platform - the codebase Nextcloud later forked from. This deployment runs the classic ownCloud Server (PHP over PostgreSQL or MariaDB, with Redis caching), the battle-tested edition trusted across enterprises, universities, and public institutions worldwide. The core loop: store files on your server, sync them via desktop clients for Windows, macOS, and Linux plus iOS and Android apps, and access everything through the web interface or standard WebDAV. Sharing is granular - internal users and groups, external recipients via public links with passwords and expiration dates, and federated sharing that connects separate ownCloud instances into one network. Security controls include file firewall rules, multi-factor authentication, encryption, and detailed audit-friendly lifecycle management with versioning and trash-bin recovery. An app marketplace extends the platform, and Web Office integrations bring collaborative document editing through Collabora Online, OnlyOffice, or Microsoft Office Online directly into your files. LDAP and Active Directory integration slots it into existing identity infrastructure. For teams that need a proven, self-hosted alternative to Dropbox or Google Drive - where compliance demands knowing exactly which disk your data sits on - ownCloud remains a foundational choice.