Top Open Source Projects using Java

A curated collection of the 46 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.

Immich

A self-hosted photo and video backup service with mobile apps, facial recognition and search across metadata, objects and faces.

Alternative to:

Apple iCloud Photos

Self-hosted photo and video backup for your own server

Stars
113,547
Forks
6,829
Last commit
5 days ago

Uptime Kuma

Self-hosted monitoring tool that checks whether your sites, servers and containers are up and tells you the moment they are not.

Alternative to:

UptimeRobot

Self-hosted uptime monitoring with a clean dashboard

Stars

Joplin

An offline-first note and to-do app in Markdown, synced with end-to-end encryption across desktop, mobile and the cloud you choose.

Alternative to:

Evernote

Encrypted note-taking that syncs across all your devices

Stars
56,260

Penpot

A design and prototyping platform for product teams, self-hostable and built on open web standards rather than a proprietary format.

Alternative to:

Framer

Open-source UI design and prototyping for product teams

Stars
59,676

DBeaver

Cross-platform desktop database tool for developers, administrators and analysts, with SQL editing, data browsing and support for over 100 drivers.

Alternative to:

DataGrip

Free database manager for SQL databases and beyond

Stars
51,679

Logseq

Privacy-first outliner for knowledge management and collaboration, storing notes as local Markdown or Org-mode files you keep control of.

Alternative to:

Notion

Privacy-first knowledge base that connects your notes

Stars
44,802

CopilotKit

SDK for developers building agent-native apps, adding chat, generative UI, shared state and human-in-the-loop across web, mobile and chat platforms.

Alternative to:

Voiceflow

Build AI copilots for your product in hours, not months

Stars

Continue

Coding agent for VS Code, JetBrains and the terminal, now shipped as a final version and no longer under active development.

Alternative to:

Cursor

Open-source coding agent for your IDE and terminal

Stars
35,812

Tabby

Self-hosted AI coding assistant that runs on consumer GPUs, an on-premises alternative for teams that cannot send code to a cloud.

Alternative to:

Cursor

AI-powered code completion for seamless development

Stars
33,869

Actual

A local-first envelope budgeting app you own end to end, syncing across devices and running on your desktop or your own server.

Alternative to:

Monarch Money

Local-first envelope budgeting with full data ownership

Stars
28,596

Jitsi

A set of open source projects for running video conferences in the browser, self-hosted or on a free public instance.

Alternative to:

Microsoft Teams

Private, secure video calls with no account needed

Stars
29,884

Signal

Private messenger for Android that uses your data connection, with encryption always on for messages, voice and video calls.

Alternative to:

WhatsApp

Private messaging with end-to-end encryption

Stars
29,307

Turso

In-process SQL database written in Rust, compatible with SQLite and now carrying a Postgres frontend, for embedded workloads.

SQLite-compatible database for scalable multi-tenant applications

Stars
24,201
Forks
1,316

Super Productivity

Todo app with timeboxing and time tracking that imports tasks from calendars, Jira and GitHub, for people juggling several systems.

Alternative to:

Toggl Track

Task manager built for deep work, privacy, and focus

Stars

Apache APISIX

Dynamic API gateway built on NGINX and etcd, handling traffic routing, security and LLM proxying for microservice platforms.

Alternative to:

Amazon API Gateway

High-performance API gateway with built-in LLM support

Stars

Scalar

Toolkit that renders OpenAPI documents as an interactive API reference and pairs it with an offline-first API client.

Alternative to:

Postman

Open-source API documentation and testing platform

Stars
16,069

Organic Maps

Offline maps and navigation built on OpenStreetMap data, made for hikers, cyclists and drivers who want no ads, tracking or data collection.

Alternative to:

Apple Maps

Privacy-first offline maps for hiking, cycling & navigation

Stars

AITable

A visual database and spreadsheet with a full REST API, for teams replacing scattered trackers with one collaborative source of records.

Alternative to:

Coda

Visual database for workflow automation across apps

Stars
15,588

Logstash

A server-side pipeline that ingests data from many sources at once, transforms it and ships it wherever your logs and events need to land.

Alternative to:

Splunk

Centralize, transform, and stash your data

Stars
14,934

Notesnook

End-to-end encrypted note taking across web, desktop and mobile, for people who want privacy without giving up a usable app.

Alternative to:

Notion

Zero-knowledge encrypted notes that sync across all devices

Stars
14,534

AutoMQ

A stateless Kafka alternative that keeps data on S3, aimed at teams paying too much to run Kafka in the cloud.

Alternative to:

Confluent Cloud

S3-based serverless Kafka reinvented for cost efficiency

Stars
10,636

LanguageTool

An open source proofreading engine for more than 25 languages, for writers and developers who want checking on a server they control.

Alternative to:

Grammarly

AI-powered grammar checker for 30+ languages

Stars
14,986

Zotero

A free reference manager that collects sources while you browse, organizes and annotates them, and generates citations in over 9,000 styles.

Alternative to:

EndNote

Collect, organize, cite, and share research in one place

Stars
15,178

Sure.am

A community-maintained personal finance and wealth management app you self-host, continuing the codebase abandoned by Maybe Finance.

Alternative to:

Monarch Money

The personal finance app for everyone

Stars
9,754

Aegis Authenticator

A free and open source 2FA app for Android with an encrypted vault, imports from other authenticators, and backups you control.

Alternative to:

Authy

2FA token manager for Android with encrypted vault

Stars

Expensify

The React Native codebase behind the New Expensify app, shipping to web, iOS and Android from one repository.

Alternative to:

Brex

Simplify expense management for businesses of all sizes

Stars
5,020

Highlight

Fullstack monitoring for web teams, pairing session replay with error tracking, logs and traces behind a few lines of setup.

Alternative to:

Datadog

Real-time observability for modern web applications

Stars
9,372

OSMAnd

A map and navigation app built on OpenStreetMap data stored offline, for drivers, cyclists and hikers who cannot rely on a connection.

Alternative to:

Apple Maps

Navigate anywhere with detailed offline maps and GPS

Stars
5,961

Apache IoTDB

A time series database for industrial IoT, handling device data at high ingest rates and analysis through a SQL-like query language.

Alternative to:

Amazon Timestream

Time-series database built for industrial IoT workloads

Stars

Tuta

An email service with end-to-end encryption built in, with open source clients for mobile, desktop and the browser for privacy-conscious users.

Alternative to:

Google Workspace

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

Stars

CloudQuery

A cloud asset inventory for platform teams that syncs infrastructure and SaaS metadata into your own warehouse for SQL analysis.

Alternative to:

Fivetran

Sync and transform data from any source to any destination

Stars
6,512

Standard Notes

An end-to-end encrypted notes app that syncs across desktop, mobile and web for people who want their notes unreadable to the host.

Alternative to:

Notion

Secure, encrypted notes for your digital life

Stars
6,622

Tolgee

Localization platform where developers edit translations in context inside the running app, with screenshots, translation memory and machine translation.

Alternative to:

Crowdin

Open-source localization platform for multilingual apps

Stars
4,092

CrateDB

Distributed SQL database for storing and querying huge volumes of data in real time, including time series, full-text search and geospatial types.

Alternative to:

Amazon Timestream

Scalable SQL database for real-time analytics

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Top Open Source Projects using Java

A curated collection of the 46 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.

Immich

Uptime Kuma

Joplin

Penpot

DBeaver

Logseq

CopilotKit

Continue

Tabby

Actual

Jitsi

Signal

Turso

Super Productivity

Apache APISIX

Scalar

Organic Maps

AITable

Logstash

Notesnook

AutoMQ

LanguageTool

Zotero

Sure.am

Aegis Authenticator

Expensify

Highlight

OSMAnd

Apache IoTDB

Tuta

CloudQuery

Standard Notes

Tolgee

CrateDB

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