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.
Open-source localization platform for multilingual apps
Stars
4,083Last commit
7 hours agoLicense
Apache-2.0
Manage app translations with in-context editing, AI translation, and collaborative tools. Self-hostable and free to start.
Open Source Alternative to:
Free 2D and 3D game engine for cross-platform projects
Stars
116,388Last commit
1 day 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
90,775Last commit
21 hours 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:
The leading distributed search and analytics engine
Stars
77,882Last commit
5 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
76,094Last commit
3 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
72,024Last commit
2 days 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
65,908Last commit
4 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:
Encrypted note-taking that syncs across all your devices
Stars
56,168Last commit
5 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:
Open-source UI design and prototyping for product teams
Stars
59,390Last commit
2 days agoLicense
MPL-2.0
Design, prototype, and hand off to developers in one platform. Supports design systems, tokens, flexible layouts, and AI workflows with real CSS/HTML output.
Open Source Alternative to:
Lightning-fast analytics for massive datasets
Stars
49,542Last commit
3 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
51,593Last commit
6 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:
Privacy-first knowledge base that connects your notes
Stars
44,690Last commit
1 day 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:
Open-source coding agent for your IDE and terminal
Stars
35,702Last commit
16 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:
Empower your team to build custom internal tools rapidly
Stars
40,785Last commit
1 day agoLicense
Apache-2.0
Low-code platform for creating powerful internal tools and dashboards with drag-and-drop ease, robust integrations, and customizable workflows.
Open Source Alternative to:
Your personal distributed filesystem
Stars
38,876Last commit
1 month agoLicense
AGPL-3.0
A cross-platform file manager that unifies your devices into a seamless, organized digital workspace.
Open Source Alternative to:
AI second brain for research, automation, and personal agents
Stars
36,797Last commit
29 days agoLicense
AGPL-3.0
Self-hostable AI assistant that connects to your docs and the web, lets you build agents, schedule automations, and run research with verifiable citations.
Open Source Alternative to:
Secure authentication and access control made simple
Stars
36,499Last commit
18 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:
AI-powered code completion for seamless development
Stars
33,843Last commit
2 months agoLicense
Apache-2.0
Self-hosted AI coding assistant that enhances productivity with context-aware suggestions and privacy-focused implementation.
Open Source Alternative to:
Advanced vulnerability detection and management platform
Stars
30,939Last commit
5 days agoLicense
MIT
Monitor infrastructure for exploitable vulnerabilities with real-time detection, automated workflows, and zero false positives.
Open Source Alternative to:
Secure access management for modern IT infrastructure
Stars
31,476Last commit
2 days agoLicense
GPL-3.0
Open-source privileged access management solution offering secure, browser-based access to SSH, RDP, Kubernetes, databases and remote applications.
Open Source Alternative to:
Transform natural language into SQL queries with AI
Stars
28,053Last commit
2 days agoLicense
Apache-2.0
AI-powered SQL client that converts natural language to SQL queries. Supports MySQL, Redis, MongoDB with Text2SQL, BI dashboards, and secure database management.
Open Source Alternative to:
Secure, private photo storage and sharing solution
Stars
28,577Last commit
2 days agoLicense
AGPL-3.0
End-to-end encrypted cloud storage for photos and videos, offering privacy, security, and seamless cross-device syncing.
Open Source Alternative to:
Private, secure video calls with no account needed
Stars
29,837Last commit
2 days agoLicense
Apache-2.0
Host encrypted video conferences directly in your browser, deploy on your own servers, or integrate into applications - all with this powerful open source platform.
Open Source Alternative to:
Declarative workflow orchestration for data, AI, and infra
Stars
27,952Last commit
9 hours agoLicense
Apache-2.0
YAML-based orchestration platform with 1400+ plugins for running data pipelines, AI workflows, and infrastructure automation across teams at scale.
Open Source Alternative to:
Private messaging with end-to-end encryption
Stars
29,268Last commit
3 days agoLicense
AGPL-3.0
Secure messaging app with state-of-the-art encryption, voice/video calls, group chats, and file sharing. No ads, trackers, or data collection.
Open Source Alternative to:
Time-series database and historian for industrial data
Stars
25,094Last commit
3 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:
Open-source data integration for modern teams
Stars
21,972Last commit
10 hours agoLicense
Elastic-2.0
Seamlessly sync data from any source to any destination with a flexible, extensible platform that grows with your data needs.
Open Source Alternative to:
Serverless Postgres for modern applications
Stars
23,000Last 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:
Task manager built for deep work, privacy, and focus
Stars
21,671Last commit
8 hours agoLicense
MIT
Combines task management, time tracking, Pomodoro focus sessions, and GitHub/Jira integration in a local-first app for Windows, macOS, Linux, Android, and iOS.
Open Source Alternative to:
Scalable open-source distributed storage system
Stars
16,977Last commit
5 hours agoLicense
Unknown
Ceph provides unified object, block, and file storage from a single cluster built on commodity hardware.
Open Source Alternative to:
SQLite-compatible database for scalable multi-tenant applications
Stars
17,183Last commit
4 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:
Professional audio editing made simple and free
Stars
17,660Last commit
8 hours agoLicense
Unknown
Free, open-source audio editor and recorder for all platforms. Record, edit, mix and enhance audio with professional tools. Perfect for music, podcasts, and more.
Open Source Alternative to:
Privacy-first offline maps for hiking, cycling & navigation
Stars
15,253Last commit
7 hours agoLicense
Apache-2.0
Free, open-source offline maps app with detailed trails, turn-by-turn navigation, and zero tracking. Perfect for hikers, cyclists, and travelers seeking privacy.
Open Source Alternative to:
High-performance time-series database for massive data scale
Stars
17,292Last commit
6 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:
Open-source search and analytics at enterprise scale
Stars
13,605Last commit
2 days agoLicense
Apache-2.0
Community-driven, Apache 2.0-licensed search and analytics suite for ingesting, searching, visualizing, and analyzing data at scale with AI/ML capabilities.
Open Source Alternative to:
Secure, customizable authentication for your applications
Stars
15,291Last commit
5 hours agoLicense
Unknown
Open-source authentication solution offering flexible, self-hosted user management with advanced features and easy integration.
Open Source Alternative to:
Zero-knowledge encrypted notes that sync across all devices
Stars
14,482Last commit
2 days agoLicense
GPL-3.0
End-to-end encrypted note-taking app with zero-knowledge architecture, cross-device sync, web clipper, and a self-hostable sync server.
Open Source Alternative to:
Centralize, transform, and stash your data
Stars
14,929Last commit
3 days agoLicense
Unknown
Logstash is a free and open server-side data processing pipeline that ingests data from multiple sources, transforms it, and sends it to your desired destination.
Open Source Alternative to:
Real-time analytics database for sub-second OLAP queries
Stars
14,047Last commit
19 hours agoLicense
Apache-2.0
Columnar, time-indexed analytics database built for streaming and batch data at scale, handling billions to trillions of rows with millisecond query response times.
Open Source Alternative to:
Visual database for workflow automation across apps
Stars
15,581Last commit
10 months agoLicense
AGPL-3.0
AITable.ai offers a visual database platform that simplifies workflow automation and connects to over 6,000 apps through integrations like Zapier and Make.
Open Source Alternative to:
AI-powered grammar checker for 30+ languages
Stars
14,894Last commit
14 hours agoLicense
LGPL-2.1
Check grammar, punctuation, and spelling errors instantly with AI-powered technology. Supports 30+ languages with browser extensions and desktop apps.
Open Source Alternative to:
Realtime client-side database for collaborative apps
Stars
10,498Last commit
16 hours agoLicense
Apache-2.0
Instant is a database solution for building real-time and offline-enabled applications, simplifying the development of collaborative products.
Open Source Alternative to:
Sevalla – Deploy your app before your coffee gets cold. It’s that easy. Try Sevalla with $50 free credit.
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