Free
JUnit
Open SourceUnit & Component · Testing
The standard testing framework for the JVM: annotation-driven unit tests for Java and Kotlin.
testingjavajvmunit-testing
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Unit & Component · Testing
The standard testing framework for the JVM: annotation-driven unit tests for Java and Kotlin.
Notebooks & Data Science · Data & Analytics
The standard interactive notebooks for data science and ML.
CLI Tools · Development Environment
Handy, syntax-clean command runner for project-specific recipes.
JWT · Encoding & Decoding
The official JSON Web Token site: decode, debug and find libraries.
Load & Performance · Testing
Open-source load testing tool using JavaScript test scripts.
Orchestration · DevOps
Terminal UI to interact with and manage Kubernetes clusters.
Notebooks & Data Science · Data & Analytics
Data science community with datasets, notebooks and competitions.
Penetration Testing · Security
Debian-based Linux distribution shipping 600+ preinstalled penetration testing and forensics tools.
Screenshots · Image & Media
Beautiful open-source screen recorder for macOS — captures, trims and exports GIFs/MP4s with plugins.
Authentication · API Tools
Open-source identity and access management with SSO and SAML.
Models & LLM APIs · AI for Developers
Moonshot AI's assistant with long-context understanding.
Web Servers & Proxies · DevOps
Popular open-source API gateway and microservices management.
Programming Languages
Official Kotlin language site: docs, playground and standard library reference.
Cross-Platform · Mobile Development
Share Kotlin code across iOS, Android, desktop and web.
Orchestration · DevOps
Template-free customization of Kubernetes YAML manifests.
ORMs · Backend
Type-safe SQL query builder for TypeScript, no DSL required.
Agent & LLM Frameworks · AI for Developers
Framework for building LLM applications with agents and chains.
Agent & LLM Frameworks · AI for Developers
Open-source LLM observability: traces, evals and prompt management.
Agent & LLM Frameworks · AI for Developers
Build stateful, multi-agent AI applications as graphs.
Feature Flags · DevOps
The commercial standard for feature flags — targeting, rollouts, experimentation and SDKs for every stack.
Payments · API Tools
Merchant-of-record payments and licensing for digital products.
Models & LLM APIs · AI for Developers
Open-source, multi-provider chat UI with agents and artifacts.
Internationalization · Frontend
Developer-friendly i18n for React and Node — readable message catalogs, macros and automatic extraction.
VPS & Bare Metal · Cloud Platforms
Akamai's cloud computing service with simple Linux VMs.