Open Source Projects using C
A curated collection of the 125 best open source software using C. Find the most popular and trending open source projects to learn from, contribute to, or use in your own projects.
Team chat with email, tasks, and docs in one workspace
Stars
3,991Last commit
10 hours agoLicense
AGPL-3.0
Team chat app with inline threads, mention-based sharing, a unified inbox for chat and email, and an AI agent that works across your full workspace.
Open Source Alternative to:
Task management with GitHub sync and AI agents for devs
Stars
3,991Last commit
10 hours agoLicense
AGPL-3.0
Task manager built for engineering teams, combining status tracking, priority management, GitHub integration, and AI agents that can close tasks automatically.
Open Source Alternative to:
Keyboard-first email client with AI, chat, and tasks
Stars
3,991Last commit
10 hours agoLicense
AGPL-3.0
An AI-powered email client that combines inbox management, chat, tasks, and AI agents in one shared workspace, built for keyboard-driven workflows.
Open Source Alternative to:
A self-building CRM powered by your email
Stars
3,991Last commit
10 hours agoLicense
AGPL-3.0
Automatically creates and enriches contacts, companies, and deal threads from your team's email. No data entry, no imports, no admin overhead.
Open Source Alternative to:
Markdown docs wired into tasks, email, and agents
Stars
3,991Last commit
10 hours agoLicense
AGPL-3.0
Collaborative markdown documents with real-time CRDT editing, AI agent cursors, mention linking, and built-in properties tied to your tasks, channels, and email.
Open Source Alternative to:
Private AI chat with zero-access encryption
Stars
5,560Last commit
2 days agoLicense
GPL-3.0
AI chat assistant from Proton that stores conversations with zero-access encryption, never logs chats, and never uses your data to train models.
Open Source Alternative to:
Run open-source LLMs locally on your own machine
Stars
179,260Last commit
1 day agoLicense
MIT
Runs open-source language models locally with a simple setup, plus optional cloud access for larger models when local hardware isn't enough.
Open Source Alternative to:
Run LLMs locally with minimal setup, maximum hardware support
Stars
125,296Last commit
9 hours agoLicense
MIT
C/C++ inference engine for large language models, supporting quantization, multi-GPU, Apple Silicon, and an OpenAI-compatible server across a wide range of hardware.
Open Source Alternative to:
Self-hosted remote desktop you fully control
Stars
121,576Last commit
2 days agoLicense
AGPL-3.0
Cross-platform remote desktop software that runs on your own servers, giving you full data control as a direct alternative to TeamViewer and AnyDesk.
Open Source Alternative to:
Minimal terminal coding agent you can fully customize
Stars
95,841Last commit
16 hours agoLicense
MIT
Terminal-based coding agent with a minimal core, 15+ LLM providers, tree-structured session history, and a TypeScript extension system for building your own workflows.
Open Source Alternative to:
Org chart, budgets, and governance for AI agent teams
Stars
79,230Last commit
10 hours agoLicense
MIT
Manages teams of AI agents across business functions with org charts, goal alignment, cost tracking, ticket tracing, and board-level governance controls.
Open Source Alternative to:
Self-hosted photo and video backup for your own server
Stars
112,435Last commit
9 hours agoLicense
AGPL-3.0
Back up, organize, search, and browse your personal photo and video library on your own server, with no third-party cloud access.
Open Source Alternative to:
Free 2D and 3D game engine for cross-platform projects
Stars
116,040Last commit
2 days agoLicense
MIT
Build 2D, 3D, and XR games with a full-featured engine that includes its own scripting language, scene editor, and export tools for multiple platforms.
Open Source Alternative to:
Postgres-powered backend platform for production apps
Stars
108,319Last commit
18 hours agoLicense
Apache-2.0
Provides a full backend stack built on Postgres: authentication, auto-generated APIs, edge functions, realtime subscriptions, file storage, and vector search.
Open Source Alternative to:
Share files securely across all devices without servers
Stars
89,111Last commit
3 days agoLicense
Apache-2.0
Free, open-source file sharing tool for nearby devices. Cross-platform support with end-to-end encryption, no registration required, automatic device discovery.
Open Source Alternative to:
High-performance code editor built for speed and AI
Stars
89,097Last commit
9 hours agoLicense
GPL-3.0
A Rust-built code editor from the creators of Atom and Tree-sitter, combining native performance with multiplayer collaboration and deep AI integration.
Open Source Alternative to:
The leading distributed search and analytics engine
Stars
77,853Last commit
9 hours agoLicense
Unknown
Elasticsearch is an open-source, RESTful search engine designed for scalability, reliability, and easy management.
Open Source Alternative to:
AI workspace for docs, projects, and wikis you control
Stars
75,883Last commit
13 days agoLicense
AGPL-3.0
Open source collaborative workspace combining notes, databases, and AI with full data ownership, offline support, and self-hosting options.
Open Source Alternative to:
Docs, whiteboards, and databases in one privacy-first workspace
Stars
71,798Last commit
17 hours agoLicense
MIT
An open-source, local-first knowledge base that merges structured docs, infinite whiteboards, databases, and AI into a single workspace for teams and creators.
Open Source Alternative to:
An independent browser engine built from scratch, not a fork
Stars
65,805Last commit
11 hours agoLicense
BSD-2-Clause
Open source web browser with its own engine, built from scratch without Blink, WebKit, or Gecko. Non-profit backed, no search deals, no user monetization.
Open Source Alternative to:
Real-time monitoring for systems and applications
Stars
80,267Last commit
9 hours agoLicense
GPL-3.0
Powerful, efficient, and user-friendly monitoring solution for servers, containers, and applications with instant insights and alerts.
Open Source Alternative to:
Free, open-source software for video recording and live streaming
Stars
75,350Last commit
1 day agoLicense
GPL-2.0
OBS Studio offers high-quality video recording and live streaming capabilities, supporting multiple platforms and providers.
Open Source Alternative to:
Run open-source AI models privately on your own device
Stars
77,395Last commit
1 year agoLicense
MIT
GPT4All runs open-source language models locally on Windows, macOS, and Linux with no cloud dependency, keeping your data on your machine.
Open Source Alternative to:
A modern terminal built around AI coding agents
Stars
64,468Last commit
9 hours agoLicense
AGPL-3.0
Terminal built for running AI coding agents like Claude Code, Codex, and Gemini CLI, with shared context, interactive code review, and multi-session management.
Open Source Alternative to:
Fast GPU-accelerated terminal with native UI design
Stars
60,104Last commit
10 hours agoLicense
MIT
Experience blazing-fast terminal performance with GPU acceleration and platform-native UI. Cross-platform compatibility meets modern design.
Open Source Alternative to:
Self-hosted AI runtime for text, voice, vision, and agents
Stars
48,636Last commit
9 hours agoLicense
MIT
Run LLMs, speech, image generation, and autonomous agents on your own hardware with an OpenAI-compatible API and 60+ swappable backends.
Open Source Alternative to:
Encrypted note-taking that syncs across all your devices
Stars
56,065Last commit
9 hours agoLicense
Unknown
Cross-platform note-taking app with end-to-end encryption, Markdown support, web clipping, and sync via Dropbox, OneDrive, or Joplin Cloud.
Open Source Alternative to:
Privacy-focused browser with powerful customization
Stars
44,054Last commit
12 hours agoLicense
MPL-2.0
A Firefox-based browser offering enhanced privacy, split views, and extensive customization options for a personalized browsing experience.
Open Source Alternative to:
Lightning-fast analytics for massive datasets
Stars
49,403Last commit
9 hours agoLicense
Apache-2.0
High-performance columnar OLAP database system for real-time analytics on big data, with SQL support and linear scalability.
Open Source Alternative to:
Free database manager for SQL databases and beyond
Stars
51,516Last commit
17 hours agoLicense
Apache-2.0
Cross-platform database management tool for exploring, editing, and querying SQL databases including MySQL, PostgreSQL, SQLite, MariaDB, and more.
Open Source Alternative to:
High-performance vector database for GenAI applications
Stars
45,749Last commit
9 hours agoLicense
Apache-2.0
Open-source vector database optimized for similarity search, scaling to billions of vectors with minimal performance loss
Open Source Alternative to:
Privacy-first knowledge base that connects your notes
Stars
44,574Last commit
10 hours agoLicense
AGPL-3.0
Local-first, open-source knowledge management tool with bidirectional linking, outlines, flashcards, PDF annotations, and whiteboards for building a connected second brain.
Open Source Alternative to:
Team chat, project management, and AI agents in one place
Stars
29,995Last commit
10 hours agoLicense
Apache-2.0
Workspace that combines team chat, project planning, and git management with AI agents that collaborate alongside your team on shared context.
Open Source Alternative to:
Unlock Product Insights with Open-Source Analytics
Stars
38,770Last commit
9 hours agoLicense
MIT
All-in-one product analytics platform. Track user behavior, run experiments, and make data-driven decisions to grow your product.
Open Source Alternative to:
Your personal distributed filesystem
Stars
38,836Last commit
26 days agoLicense
AGPL-3.0
A cross-platform file manager that unifies your devices into a seamless, organized digital workspace.
Open Source Alternative to:
Press a key, speak, release. Text appears instantly.
Stars
30,150Last commit
15 hours agoLicense
MIT
Cross-platform desktop app that transcribes your voice into any text field using a keyboard shortcut, with all processing done locally on your machine.
Open Source Alternative to:
Secure authentication and access control made simple
Stars
36,351Last commit
14 hours agoLicense
Apache-2.0
Comprehensive open source identity management solution offering single sign-on, social login, and fine-grained authorization for applications and services.
Open Source Alternative to:
Powerful API development and testing made effortless
Stars
39,955Last commit
3 days agoLicense
Apache-2.0
Intuitive API client for REST, GraphQL, and gRPC. Debug, test, and collaborate on APIs with ease across platforms.
Open Source Alternative to:
Zero-config VPN with WireGuard for secure networking
Stars
35,466Last commit
9 hours agoLicense
BSD-3-Clause
Deploy a modern WireGuard-based VPN with zero configuration. Connect devices securely across clouds, VPCs, and on-premises networks without firewall rules.
Open Source Alternative to:
Local AI meeting transcription with zero data leaving your device
Stars
29,782Last commit
3 months agoLicense
MIT
Records, transcribes, and summarizes meetings entirely on your device using local AI. No bots, no cloud uploads, GDPR and HIPAA compliant by design.
Open Source Alternative to:
Fast, scalable vector database for AI applications
Stars
34,143Last commit
2 days agoLicense
Apache-2.0
Qdrant is an open-source vector database that provides high-performance similarity search for AI and machine learning applications.
Open Source Alternative to:
Blazing-fast in-memory data store for modern applications
Stars
31,019Last commit
12 hours agoLicense
Unknown
Dragonfly is a high-performance, Redis-compatible in-memory data store that delivers up to 25x more throughput and 80% lower costs than legacy solutions.
Open Source Alternative to:
Docmost – Open-source wiki software with real-time collaboration, diagrams, AI, SSO, RBAC permissions and more.
Docmost
Stellar Hosted
Sent