Open Source Projects using C#
A curated collection of the 33 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
115,878Last commit
7 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
90,353Last 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
55,952Last commit
8 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
49,340Last commit
7 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
35,545Last commit
18 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
39,200Last commit
2 days 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
25,068Last commit
4 days 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
25,587Last commit
7 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
22,901Last commit
3 months 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
19,901Last commit
7 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
17,147Last commit
8 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
15,946Last commit
1 day 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
17,264Last commit
8 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
14,321Last commit
9 hours 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
11,949Last commit
8 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
9,367Last commit
1 day 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
6,408Last commit
9 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
7,481Last commit
7 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
6,381Last commit
16 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
4,543Last commit
2 days 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
4,250Last commit
8 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
4,121Last commit
4 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
3,276Last commit
17 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
2,345Last commit
9 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
2,241Last 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.
Open source monitoring for complex IT infrastructure
Stars
2,232Last commit
18 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
1,902Last commit
11 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:
Privacy-first analytics for mobile and desktop apps
Stars
1,777Last commit
7 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:
Type 10x faster with AI-powered voice dictation
Stars
1,495Last commit
22 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:
One self-hosted binary replaces Vercel, Sentry, and analytics tools
Stars
650Last commit
7 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
371Last commit
2 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
393Last commit
2 days 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
65Last commit
3 months 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:
c15t – Open-source cookie banner, built for control and lightening fast modern web apps.
c15t
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