Open Source Projects using C#
A curated collection of the 34 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.
Free 2D and 3D game engine for cross-platform projects
Stars
116,830Last commit
14 hours 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:
Self-hosted uptime monitoring with a clean dashboard
Stars
91,141Last commit
1 day agoLicense
MIT
Monitors websites, APIs, and services with real-time alerts, a status page, and support for dozens of notification channels. Self-hosted and Docker-friendly.
Open Source Alternative to:
Self-hosted media server for movies, music, and more
Stars
56,740Last commit
16 hours agoLicense
GPL-2.0
Free, open source media server that lets you collect, manage, and stream your personal library to any device, with no fees, tracking, or vendor lock-in.
Open Source Alternative to:
Lightning-fast analytics for massive datasets
Stars
49,741Last commit
12 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:
Open-source coding agent for your IDE and terminal
Stars
35,832Last commit
22 hours agoLicense
Apache-2.0
Runs source-controlled AI checks on every pull request, enforcing your engineering standards as native GitHub status checks with suggested fixes.
Open Source Alternative to:
Powerful screen capture and file sharing tool for Windows
Stars
39,500Last commit
19 hours agoLicense
GPL-3.0
ShareX is a free, open-source program that captures or records any area of your screen and shares it with a single keypress, supporting various file types and destinations.
Open Source Alternative to:
Time-series database and historian for industrial data
Stars
25,102Last commit
23 hours agoLicense
AGPL-3.0
High-performance time-series database with industrial data management, built-in stream analytics, and AI-driven anomaly detection for operational environments.
Open Source Alternative to:
Infrastructure as code in your favorite language
Stars
25,658Last commit
12 hours agoLicense
Apache-2.0
Pulumi enables developers to define and manage cloud infrastructure using familiar programming languages instead of domain-specific languages.
Open Source Alternative to:
Serverless Postgres for modern applications
Stars
23,057Last commit
9 days agoLicense
Apache-2.0
Cloud-native, auto-scaling Postgres with instant branching, bottomless storage, and pay-per-use pricing
Open Source Alternative to:
Secure password management for individuals and businesses
Stars
20,097Last commit
13 hours agoLicense
Unknown
Bitwarden is an open source password manager that securely stores, shares, and autofills passwords across unlimited devices.
Open Source Alternative to:
SQLite-compatible database for scalable multi-tenant applications
Stars
17,209Last commit
14 days agoLicense
MIT
Turso provides a simple developer experience with SQLite compatibility, allowing you to build and scale multi-tenant applications with unlimited databases.
Open Source Alternative to:
Open-source API documentation and testing platform
Stars
16,082Last commit
15 hours agoLicense
MIT
Scalar is an open-source tool for building, customizing, and hosting interactive API documentation with OpenAPI support.
Open Source Alternative to:
High-performance time-series database for massive data scale
Stars
17,311Last commit
13 hours agoLicense
Apache-2.0
Open-source time-series database offering massive ingestion throughput, millisecond queries, and SQL extensions, designed for optimal performance at any hardware scale.
Open Source Alternative to:
Free, open-source framework for cross-platform game development
Stars
14,401Last commit
4 days agoLicense
Unknown
Build games in C# that run on Windows, macOS, Linux, iOS, Android, and major consoles. No royalties, no subscriptions, no runtime fees.
Open Source Alternative to:
Lightning-fast open source search engine for big data
Stars
11,995Last commit
14 hours agoLicense
GPL-3.0
Open source search database delivering 2.83x faster performance than Elasticsearch. Features vector search, SQL interface, and full-text capabilities.
Open Source Alternative to:
Real-time observability for modern web applications
Stars
9,372Last commit
19 days agoLicense
Apache-2.0
Comprehensive monitoring solution offering error tracking, session replay, and performance insights for seamless debugging and optimization.
Open Source Alternative to:
Build and play games inside a game engine that runs live
Stars
6,454Last commit
12 hours agoLicense
MIT
A game creation platform built on Valve's Source 2 engine, letting you build, share, and play games without leaving the environment.
Open Source Alternative to:
Comprehensive monitoring and incident management platform
Stars
7,570Last commit
12 hours agoLicense
Apache-2.0
All-in-one solution for uptime monitoring, incident management, and status pages to keep your services running smoothly
Open Source Alternative to:
Time-series database built for industrial IoT workloads
Stars
6,391Last commit
19 hours agoLicense
Apache-2.0
Apache IoTDB manages industrial IoT time-series data with high-throughput read/write, edge-cloud sync, ultra-high compression, and integrations with Hadoop, Spark, Flink, and Grafana.
Open Source Alternative to:
Secure, policy-based access control for modern applications
Stars
4,578Last commit
18 hours agoLicense
Apache-2.0
A scalable authorization layer that provides fine-grained access control through externalized policies, enabling secure and flexible permissions management.
Open Source Alternative to:
Free office suite with Microsoft compatibility
Stars
4,335Last commit
14 hours agoLicense
GPL-3.0
Complete free office suite compatible with Microsoft formats (.doc, .docx, .xls, .xlsx, .ppt, .pptx). Open source alternative with regular updates.
Open Source Alternative to:
Professional raw photo processing made free and powerful
Stars
4,160Last commit
12 days agoLicense
GPL-3.0
Free, cross-platform raw image processor with 32-bit floating point engine, advanced demosaicing algorithms, and professional-grade editing tools for photographers.
Open Source Alternative to:
Secure, decentralized cloud storage for your data
Stars
3,279Last commit
13 hours agoLicense
AGPL-3.0
Storj offers a distributed cloud storage platform with enhanced security, global performance, and significant cost savings compared to traditional providers.
Open Source Alternative to:
Complete IT infrastructure monitoring made simple
Stars
2,359Last commit
12 hours agoLicense
GPL-2.0
Monitor your entire IT infrastructure with 2,000+ plugins, automated discovery, and scalable architecture. Open source and enterprise solutions available.
Open Source Alternative to:
Real-time stream processing made simple and affordable
Stars
2,253Last commit
7 days agoLicense
Apache-2.0
Timeplus is a lightweight, powerful, and cost-efficient stream processing platform for real-time analytics, deployed as a single binary.
Business rules engine with AI, visual flows, and audit trails
Stars
1,968Last commit
15 days agoLicense
MIT
Model business logic in decision tables, visual flows, and natural-language rules. Change rules without deploys, test every path, and run the same engine anywhere.
Open Source Alternative to:
Open source monitoring for complex IT infrastructure
Stars
2,236Last commit
19 hours agoLicense
GPL-3.0
Monitor networks, servers, and cloud environments with flexible open-source solution. Custom checks, fast alerts, and complete infrastructure control.
Open Source Alternative to:
Open-source feature flag management for seamless deployments
Stars
1,906Last commit
20 hours agoLicense
MIT
FeatBit is a fast, scalable feature flag service that enables risk mitigation and fosters business growth through controlled feature releases.
Open Source Alternative to:
Type 10x faster with AI-powered voice dictation
Stars
1,525Last commit
4 days agoLicense
MIT
Open source AI dictation app that transforms speech to text with context-aware formatting. Fast, accurate transcription for meetings, notes, and hands-free typing.
Open Source Alternative to:
Privacy-first analytics for mobile and desktop apps
Stars
1,795Last commit
27 days agoLicense
AGPL-3.0
Open-source, self-hostable analytics platform for mobile and desktop apps, prioritizing user privacy and data control.
Open Source Alternative to:
One self-hosted binary replaces Vercel, Sentry, and analytics tools
Stars
729Last commit
12 hours agoLicense
Apache-2.0
Self-hosted platform for small dev teams combining deployments, error tracking, analytics, session replay, uptime monitoring, and managed databases in one dashboard.
Open Source Alternative to:
Fast, secure, and privacy-focused web browsing
Stars
391Last commit
4 days agoLicense
MPL-2.0
Midori Browser is a lightweight, fast, and secure browser that protects users' privacy, available for Windows, Linux, and Android.
Open Source Alternative to:
Community-driven platform built for transparency
Stars
396Last commit
1 day agoLicense
AGPL-3.0
Open-source communication platform with multi-window chat, economy systems, and privacy-first approach. Built by communities for superior performance.
Open Source Alternative to:
Transcribe meetings and voice notes with local AI, no bots required
Stars
77Last commit
15 hours agoLicense
MIT
Free, open-source AI note-taker that transcribes meetings and voice notes locally using Whisper and Parakeet. Works on Mac, Windows, and mobile without invasive bots.
Open Source Alternative to:
Openlane – Open-source, developer-first platform for automated compliance, risk management, and built-in Trust Center.
Openlane
Stellar Hosted
ScreenshotOne