Free
Jaeger
Open SourceAPM & Tracing · Monitoring & Observability
Open-source distributed tracing platform, CNCF graduated.
tracingdistributedobservability
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APM & Tracing · Monitoring & Observability
Open-source distributed tracing platform, CNCF graduated.
Models & LLM APIs · AI for Developers
Open-source ChatGPT alternative that runs LLMs fully offline on your machine, with an OpenAI-compatible API.
Programming Languages
Official Java developer portal with documentation, tutorials and downloads.
References · Documentation & Learning
The Modern JavaScript Tutorial — the deepest free JS reference from basics to advanced browser APIs.
CI/CD · DevOps
The classic open-source automation server for CI/CD.
Unit & Component · Testing
Delightful JavaScript testing framework with snapshots and mocks.
CLI Tools · Development Environment
Lightweight command-line JSON processor.
JSON · Data Formats
Official site of the JSON Schema specification, with tools and validators.
Programming Languages
High-performance language for technical and scientific computing.
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.
Orchestration · DevOps
Terminal UI to interact with and manage Kubernetes clusters.
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.
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
Build stateful, multi-agent AI applications as graphs.
Internationalization · Frontend
Developer-friendly i18n for React and Node — readable message catalogs, macros and automatic extraction.
Models & LLM APIs · AI for Developers
Open-source LLM gateway: one API for 100+ providers.