Open Source Projects using Java
A curated collection of the 81 best open source software using Java. Find the most popular and trending open source projects to learn from, contribute to, or use in your own projects.
The personal finance app for everyone
Stars
9,655Last commit
19 hours agoLicense
AGPL-3.0
An all-in-one personal finance platform. Track, optimize, grow, and manage your money through every stage of life.
Open Source Alternative to:
2FA token manager for Android with encrypted vault
Stars
12,987Last commit
2 days agoLicense
GPL-3.0
Android app for managing two-factor authentication tokens with encrypted storage, biometric unlock, flexible backups, and import/export from major 2FA apps.
Open Source Alternative to:
Lightning-fast open source search engine for big data
Stars
11,967Last commit
6 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:
Professional digital painting made accessible to everyone
Stars
10,285Last commit
9 hours agoLicense
GPL-3.0
Free and open source painting program built by artists for artists. Features professional brushes, layers, animation tools, and drawing assistants for all skill levels.
Open Source Alternative to:
Real-time observability for modern web applications
Stars
9,373Last commit
10 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:
Simplify expense management for businesses of all sizes
Stars
5,015Last commit
3 hours agoLicense
MIT
Automate expense reporting, reimbursements, and corporate card management with real-time data sync and powerful integrations.
Security-first diagramming with no login required
Stars
7,808Last commit
2 days agoLicense
Apache-2.0
Create professional diagrams online or offline with security-first approach. No registration needed. Works with Google Drive, SharePoint, Atlassian, and more.
Open Source Alternative to:
Secure email, calendar and contacts with end-to-end encryption
Stars
7,882Last commit
2 days agoLicense
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:
Time-series database built for industrial IoT workloads
Stars
6,386Last commit
15 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:
Sync and transform data from any source to any destination
Stars
6,503Last commit
2 days agoLicense
MPL-2.0
CloudQuery is an open-source ELT platform that enables easy data integration from hundreds of cloud and security tools to any destination.
Open Source Alternative to:
Enterprise monitoring for networks, apps, and infrastructure
Stars
6,321Last commit
2 days agoLicense
AGPL-3.0
Monitors networks, servers, cloud services, IoT, and OT environments with no per-device licensing fees, available self-hosted or as a managed SaaS platform.
Open Source Alternative to:
Distributed OLAP database for real-time analytics at scale
Stars
6,128Last commit
12 hours agoLicense
Apache-2.0
Sub-second SQL queries on fresh streaming data at petabyte scale, built for high-concurrency user-facing apps and AI agent backends.
Open Source Alternative to:
Secure, encrypted notes for your digital life
Stars
6,614Last commit
5 days agoLicense
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:
Build scalable authorization in minutes, not months
Stars
5,942Last commit
2 days agoLicense
AGPL-3.0
Open-source authorization service for implementing fine-grained access controls. Centralized, scalable solution supporting RBAC, ABAC and ReBAC with Google Zanzibar-inspired architecture.
Open Source Alternative to:
Navigate anywhere with detailed offline maps and GPS
Stars
5,942Last commit
6 hours agoLicense
Unknown
Comprehensive offline navigation app with detailed maps, turn-by-turn guidance, and specialized routing for hiking, cycling, and walking worldwide.
Open Source Alternative to:
Secure, policy-based access control for modern applications
Stars
4,563Last 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
4,289Last commit
7 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:
Scalable SQL database for real-time analytics
Stars
4,431Last commit
5 hours agoLicense
Apache-2.0
Distributed SQL database designed for high-speed ingestion and complex queries on massive datasets, ideal for IoT and time-series data.
Open Source Alternative to:
Open-source document editing suite for secure collaboration
Stars
3,331Last commit
3 days agoLicense
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:
Open-source code security engine for developers
Stars
3,007Last commit
3 hours agoLicense
LGPL-2.1
Opengrep is a community-driven fork of SemgrepCE, providing accessible static code analysis and security scanning for developers.
Serverless team chat over Tor, no phone number needed
Stars
2,641Last commit
3 days agoLicense
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:
Real-time stream processing made simple and affordable
Stars
2,250Last commit
18 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
1,951Last commit
5 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:
Secure, private, and decentralized file storage
Stars
2,453Last commit
20 hours agoLicense
AGPL-3.0
A peer-to-peer encrypted filesystem for secure file storage, sharing, and collaboration with end-to-end encryption and user-controlled data.
Open Source Alternative to:
Track your TV shows and movies on Android
Stars
2,148Last commit
2 days agoLicense
Unknown
Android app for tracking TV shows and movies you're watching, have watched, or plan to watch, powered by TMDb data.
Open Source Alternative to:
Create custom spaces to chat, game, and connect globally
Stars
1,667Last commit
14 hours agoLicense
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:
Local-first 2FA authenticator and password manager
Stars
1,498Last commit
1 day agoLicense
GPL-3.0
Open-source authenticator and password manager that stores 2FA tokens and passwords locally on your device, with zero-knowledge encryption and no account required.
Open Source Alternative to:
Open-source knowledge management and collaboration platform
Stars
1,302Last commit
12 hours agoLicense
LGPL-2.1
XWiki is a flexible, feature-rich wiki software that helps organizations structure and share knowledge efficiently.
Open Source Alternative to:
Unify APIs, databases, and services effortlessly
Stars
1,257Last commit
16 hours agoLicense
Apache-2.0
A powerful backend framework that simplifies API integration, enhances security, and boosts developer productivity for modern web applications.
Open Source Alternative to:
Track TV shows and movies, synced with Trakt.tv
Stars
1,454Last commit
2 months agoLicense
GPL-3.0
Android and iOS app for tracking TV shows and movies, managing watchlists, and syncing viewing history with Trakt.tv across devices.
Open Source Alternative to:
Build AI agents and automate complex workflows seamlessly
Stars
994Last commit
3 days agoLicense
Apache-2.0
Create intelligent automation workflows combining AI agents with your favorite apps and services. Connect, automate, and scale your operations without complex coding.
Open Source Alternative to:
One self-hosted binary replaces Vercel, Sentry, and analytics tools
Stars
700Last commit
4 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:
Build complete web apps with integrated graph database
Stars
828Last commit
20 days agoLicense
Unknown
Open-source low-code platform combining Neo4j graph database, visual schema editor, automatic REST APIs, and page rendering in one self-hosted environment.
Secure open source email with advanced encryption & AI
Stars
651Last commit
15 hours agoLicense
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:
Unified API, event, and AI agent management platform
Stars
447Last commit
14 hours agoLicense
Apache-2.0
Full-lifecycle API management platform that unifies synchronous and asynchronous ecosystems. Manage APIs, event streams, and AI agents with enterprise security and 4x faster gateway performance.
Open Source Alternative to:
Open-source ideation tool for product feedback management
Stars
451Last commit
1 day agoLicense
Apache-2.0
ClearFlask is an open-source platform for collecting, analyzing, and acting on customer feedback to drive product development.
Open Source Alternative to:
Fast, secure, and privacy-focused web browsing
Stars
384Last commit
16 hours 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:
Connect APIs, databases, and streams without glue code
Stars
361Last commit
2 months agoLicense
Unknown
Automated data integration platform that connects APIs, databases, and event streams using semantic schemas. Deploy secure integrations in minutes with Git-based workflows.
Open Source Alternative to:
OTA updates for Capacitor apps without app store delays
Stars
205Last commit
4 hours agoLicense
AGPL-3.0
Live update platform for Ionic and Capacitor apps that pushes JavaScript, CSS, and asset changes to devices in minutes, with channels, rollback, and release analytics.
Open Source Alternative to:
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