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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.

Favicon of Builder

Builder

Visual development platform for modern web experiences

  • Stars

    8,806

  • Last commit

    3 days ago

  • License

    MIT
Drag-and-drop interface for creating and optimizing digital experiences, with headless CMS and powerful integrations.

Open Source Alternative to:

Favicon of WordPress
WordPress
Favicon of FireZone

FireZone

Fast, flexible VPN replacement with zero-trust security

  • Stars

    9,039

  • Last commit

    13 hours ago

  • License

    Apache-2.0
Replace your VPN with zero-trust access built on WireGuard. Fast, scalable network security with simple policies and identity provider integration.

Open Source Alternative to:

Favicon of Zerotier
Zerotier
Favicon of s&box

s&box

Build and play games inside a game engine that runs live

  • Stars

    6,415

  • Last commit

    2 days ago

  • License

    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:

Favicon of Unity
Unity
Favicon of Activeloop

Activeloop

AI
The tensor database for AI data

  • Stars

    9,227

  • Last commit

    3 months ago

  • License

    Apache-2.0
Deep Lake is an open-source database for storing, querying and managing complex AI data like images, audio, and embeddings.

Open Source Alternative to:

Favicon of MongoDB
MongoDB
Favicon of Expensify

Expensify

Simplify expense management for businesses of all sizes

  • Stars

    5,011

  • Last commit

    9 hours ago

  • License

    MIT
Automate expense reporting, reimbursements, and corporate card management with real-time data sync and powerful integrations.
Favicon of OpenWispr

OpenWispr

AI
Voice-to-text that works offline, privately, on any app

  • Stars

    5,673

  • Last commit

    12 hours ago

  • License

    MIT
Dictation app powered by OpenAI Whisper and NVIDIA Parakeet. Runs locally on macOS, Windows, and Linux with zero data retention and 100+ language support.

Open Source Alternative to:

Favicon of Wispr Flow
Wispr Flow
Favicon of Plasmic

Plasmic

Visual app builder that integrates with your existing codebase

  • Stars

    6,968

  • Last commit

    21 hours ago

  • License

    MIT
Open-source visual editor for building websites and web apps. Connect to any data source, design custom UIs, and ship production React code without leaving your stack.

Open Source Alternative to:

Favicon of Framer
Framer
Favicon of Tuta

Tuta

Secure email, calendar and contacts with end-to-end encryption

  • Stars

    7,866

  • Last commit

    2 days ago

  • License

    GPL-3.0
Tuta offers encrypted email, calendar and contacts with quantum-resistant security, protecting your privacy without ads or tracking.

Open Source Alternative to:

Favicon of Gmail
Gmail
Favicon of Apache IoTDB

Apache IoTDB

Time-series database built for industrial IoT workloads

  • Stars

    6,383

  • Last commit

    11 hours ago

  • License

    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:

Favicon of InfluxDB
InfluxDB
Favicon of Standard Notes

Standard Notes

Secure, encrypted notes for your digital life

  • Stars

    6,598

  • Last commit

    5 days ago

  • License

    AGPL-3.0
Cross-platform note-taking app with end-to-end encryption, offline access, and powerful organization features for privacy-conscious users.

Open Source Alternative to:

Favicon of Obsidian
Obsidian
Favicon of GIMP

GIMP

Professional image editing without the price tag

  • Stars

    6,372

  • Last commit

    10 hours ago

  • License

    Unknown
Free, open-source image editor with professional tools for photo manipulation, digital art creation, and graphic design. Cross-platform support.

Open Source Alternative to:

Favicon of Adobe Photoshop
Adobe Photoshop
Favicon of Kdenlive

Kdenlive

Professional video editing without the price tag

  • Stars

    5,506

  • Last commit

    12 hours ago

  • License

    GPL-3.0
Cross-platform non-linear video editor offering professional features for free. Edit videos on Linux, Windows, macOS, and BSD with advanced tools and effects.

Open Source Alternative to:

Favicon of CapCut
CapCut
Favicon of Zen

Zen

System-wide ad-blocking and privacy protection, no extensions needed

  • Stars

    4,136

  • Last commit

    1 day ago

  • License

    MIT
Free, open-source desktop app that blocks ads, trackers, and surveillance scripts across all browsers and apps on Windows, macOS, and Linux.

Open Source Alternative to:

Favicon of AdGuard
AdGuard
Favicon of Memgraph

Memgraph

High-performance graph computing for scalable data analysis

  • Stars

    4,356

  • Last commit

    2 days ago

  • License

    Unknown
Memgraph is a scalable, in-memory graph database solution offering high-performance computing and Neo4j compatibility.

Open Source Alternative to:

Favicon of MongoDB
MongoDB
Favicon of LibreOffice

LibreOffice

Free office suite with Microsoft compatibility

  • Stars

    4,262

  • Last commit

    13 hours ago

  • License

    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:

Favicon of Microsoft Word
Microsoft Word
Favicon of Collabora Online

Collabora Online

Open-source document editing suite for secure collaboration

  • Stars

    3,324

  • Last commit

    6 days ago

  • License

    Unknown
Powerful online document editor with Microsoft Office compatibility. Integrate into your infrastructure or use trusted hosting partners for secure team collaboration.

Open Source Alternative to:

Favicon of Microsoft Word
Microsoft Word
Favicon of Opengrep

Opengrep

Open-source code security engine for developers

  • Stars

    2,979

  • Last commit

    1 day ago

  • License

    LGPL-2.1
Opengrep is a community-driven fork of SemgrepCE, providing accessible static code analysis and security scanning for developers.
Favicon of RawTherapee

RawTherapee

Professional raw photo processing made free and powerful

  • Stars

    4,126

  • Last commit

    8 days ago

  • License

    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:

Favicon of Adobe Lightroom
Adobe Lightroom
Favicon of Anthias

Anthias

Transform any TV into professional digital signage

  • Stars

    3,651

  • Last commit

    4 days ago

  • License

    Unknown
Free open-source digital signage software that turns Raspberry Pi or old PCs into powerful display solutions. Manage images, videos, and web content easily.

Open Source Alternative to:

Favicon of Yodeck
Yodeck
Favicon of OpenLIT

OpenLIT

AI
Monitor, debug, and scale LLM applications with ease

  • Stars

    2,714

  • Last commit

    4 days ago

  • License

    Apache-2.0
Open-source observability platform for GenAI and LLM applications. Real-time monitoring, distributed tracing, prompt management, and AI model evaluation built on OpenTelemetry.

Open Source Alternative to:

Favicon of LangSmith
LangSmith
Favicon of Sol

Sol

Fast and beautiful launcher for quick access to apps and tools

  • Stars

    3,075

  • Last commit

    4 days ago

  • License

    MIT
A modern macOS launcher that provides instant access to applications, utilities, and system functions through an elegant and efficient interface.

Open Source Alternative to:

Favicon of Raycast
Raycast
Favicon of Quiet

Quiet

Serverless team chat over Tor, no phone number needed

  • Stars

    2,640

  • Last commit

    3 days ago

  • License

    GPL-3.0
Quiet is a peer-to-peer messaging app that syncs messages directly between devices over Tor, with no central server, no phone number required, and no metadata leaks.

Open Source Alternative to:

Favicon of Discord
Discord
Favicon of Checkmk

Checkmk

AI
Complete IT infrastructure monitoring made simple

  • Stars

    2,348

  • Last commit

    9 hours ago

  • License

    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:

Favicon of DataDog
DataDog
Favicon of Timeplus

Timeplus

Real-time stream processing made simple and affordable

  • Stars

    2,245

  • Last commit

    11 days ago

  • License

    Apache-2.0
Timeplus is a lightweight, powerful, and cost-efficient stream processing platform for real-time analytics, deployed as a single binary.
Favicon of Icinga

Icinga

Open source monitoring for complex IT infrastructure

  • Stars

    2,232

  • Last commit

    3 days ago

  • License

    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:

Favicon of DataDog
DataDog
Favicon of GoRules

GoRules

Business rules engine with AI, visual flows, and audit trails

  • Stars

    1,938

  • Last commit

    2 days ago

  • License

    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:

Favicon of Drools
Drools
Favicon of Nagios

Nagios

Complete infrastructure monitoring with 25+ years of expertise

  • Stars

    2,040

  • Last commit

    16 days ago

  • License

    GPL-2.0
Free open source IT monitoring solution for servers, networks, and applications. Trusted by 1M+ users worldwide with powerful alerting and enterprise-grade features.

Open Source Alternative to:

Favicon of Opsgenie
Opsgenie
Favicon of Amical

Amical

AI
Type 10x faster with AI-powered voice dictation

  • Stars

    1,503

  • Last commit

    3 days ago

  • License

    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:

Favicon of Wispr Flow
Wispr Flow
Favicon of Mezon

Mezon

Create custom spaces to chat, game, and connect globally

  • Stars

    1,578

  • Last commit

    13 hours ago

  • License

    MIT
Build your own community space for gaming, chatting, and hanging out with friends worldwide. Customize your environment for the perfect social experience.

Open Source Alternative to:

Favicon of Discord
Discord
Favicon of Apache Cloudberry

Apache Cloudberry

Unlock Data's Potential with Open Source Power

  • Stars

    1,370

  • Last commit

    13 hours ago

  • License

    Apache-2.0
Leverage advanced analytics with a modern PostgreSQL kernel. 100% open source for robust data solutions.

Open Source Alternative to:

Favicon of Snowflake
Snowflake
Favicon of Terrateam

Terrateam

GitOps orchestration for infrastructure as code

  • Stars

    1,268

  • Last commit

    2 days ago

  • License

    MPL-2.0
Automate infrastructure changes with secure GitOps workflows. Plan, validate, and deploy Terraform, OpenTofu, and Pulumi directly from pull requests.

Open Source Alternative to:

Favicon of Terraform
Terraform
Favicon of Jarvis

Jarvis

AI
Dictate faster and control your Mac with voice

  • Stars

    619

  • Last commit

    3 days ago

  • License

    MIT
Free, open-source macOS voice assistant that transcribes speech, applies AI transformations, and controls apps hands-free. No subscription, no training required.

Open Source Alternative to:

Favicon of Wispr Flow
Wispr Flow
Favicon of Alarik

Alarik

S3-compatible object storage built with Swift

  • Stars

    514

  • Last commit

    5 days ago

  • License

    Apache-2.0
Self-hostable, Apache 2.0-licensed object storage with S3 compatibility, a built-in web console, and horizontal scaling from single node to sharded cluster.

Open Source Alternative to:

Favicon of Amazon S3
Amazon S3
Favicon of Twake Mail

Twake Mail

Secure open source email with advanced encryption & AI

  • Stars

    647

  • Last commit

    3 days ago

  • License

    AGPL-3.0
Open source professional email solution with PGP encryption, JMAP protocol, AI-powered responses, and advanced antispam protection. Control your data privately.

Open Source Alternative to:

Favicon of Gmail
Gmail
Favicon of Tonkatsu Box

Tonkatsu Box

Track games, movies, anime, manga, and books in one place

  • Stars

    511

  • Last commit

    3 days ago

  • License

    MIT
Cross-platform collection manager for retro games, movies, TV shows, anime, manga, visual novels, and books with tier lists, visual boards, and import/export.

Open Source Alternative to:

Favicon of TV Time
TV Time
Favicon of Browser Operator

Browser Operator

AI
Open-source AI browser for intelligent web automation

  • Stars

    499

  • Last commit

    5 months ago

  • License

    BSD-3-Clause
Privacy-focused AI browser with intelligent agents for research, analysis, and workflow automation. Features unified memory, compliance guardrails, and seamless integrations.

Open Source Alternative to:

Favicon of Comet Browser
Comet Browser
Favicon of Midori Browser

Midori Browser

Fast, secure, and privacy-focused web browsing

  • Stars

    385

  • Last commit

    20 hours ago

  • License

    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:

Favicon of Firefox
Firefox
Favicon of Prismical

Prismical

AI
Transcribe meetings and voice notes with local AI, no bots required

  • Stars

    66

  • Last commit

    3 months ago

  • License

    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:

Favicon of Granola
Granola
Favicon of Brace.to

Brace.to

Securely save and access your favorite links across devices

  • Stars

    105

  • Last commit

    4 months ago

  • License

    MIT
A privacy-focused bookmark manager that encrypts your saved links, allowing you to access them anytime, anywhere, on any device with complete control.

Open Source Alternative to:

Favicon of Pocket
Pocket
Favicon of Paralino

Paralino

End-to-end encrypted location sharing for groups

  • Stars

    53

  • Last commit

    21 days ago

  • License

    AGPL-3.0
Share your real-time location with family and friends using end-to-end encryption, geofence alerts, travel history, and multi-device tracking.

Open Source Alternative to:

Favicon of Life360
Life360
Favicon of Justnote

Justnote

Privacy-focused note-taking made simple and fast

  • Stars

    67

  • Last commit

    7 months ago

  • License

    GPL-2.0
Justnote is a secure note-taking app that lets you easily create and sync notes across devices while maintaining full control of your data.

Open Source Alternative to:

Favicon of Notion
Notion
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