Open Source⁽⁵⁷⁾

The Go programming language itself. The clearest end-to-end example of a production compiler, runtime, and standard library you can read line by line.

A modern HTTP/3 web server with automatic HTTPS via Let's Encrypt. Beautifully modular Go code showing how to build a plugin-driven server.

A blazing-fast command-line fuzzy finder. Study it for terminal UI patterns, efficient string scoring algorithms, and how to ship a single-binary CLI users actually love.

A simple terminal UI for Git. The reference implementation if you want to learn how to build interactive TUIs in Go (uses tcell + custom event loop).

Fast reverse proxy for exposing local servers behind NAT or firewalls. Masterclass on building bidirectional tunnels and connection multiplexing in Go.

The world's fastest static site generator. Read it to understand high-throughput templating, content pipelines, and how to keep a Go binary responsive at scale.

Decentralised continuous file synchronisation. The best open-source case study for peer-to-peer protocols, conflict resolution, and Merkle-tree diffs in Go.

Industry-standard metrics + time-series database. Read it to learn how to design a TSDB, build a pull-based scraper, and write a PromQL-style query engine.

Distributed key-value store powering Kubernetes. The canonical Raft consensus implementation in Go — essential reading for distributed systems.

HTML components written in pure Go — no template engine. Tiny codebase that demonstrates type-safe, composable UI generation using only the standard library.

Lodash-style utility library leveraging Go 1.18+ generics. Read it to learn how to use generics idiomatically for slices, maps, and channels.

Embedded pure-Go key-value store used inside etcd, Consul, and InfluxDB. The cleanest readable implementation of a B+ tree + mmap database engine.

Self-hostable WhatsApp CRM template — shared inbox, contacts, sales pipelines, broadcasts, no-code automations. Next.js 16 + React 19 + Supabase + Meta Cloud API. Fork it as the starting point for any WhatsApp-first product.

Lee Robinson's production-ready SaaS starter — Next.js 15 App Router, Stripe subscriptions, Postgres + Drizzle, role-based access, dashboard out of the box.

Open-source Calendly alternative built on Next.js. Massive codebase that shows how to architect a multi-tenant scheduling product end to end.

Open-source DocuSign alternative. Real production Next.js app with cryptographic signatures, PDF manipulation, and clean tRPC + Prisma architecture.

Modern open-source link shortener with analytics. Next.js + Vercel edge functions + Upstash Redis — perfect study material for edge-first product architecture.

Open-source Jira / Linear alternative. Full-stack Next.js + Django case study for ticketing, real-time collab, and complex permission models.

shadcn's reference Next.js app — exhibits the App Router, server actions, Radix UI patterns, and the original blueprint that shadcn/ui was built from.

Provider-agnostic TypeScript SDK for streaming text, structured outputs, and tool calling. The foundation of nearly every modern Next.js AI feature.

Run Llama, Mistral, Gemma and other LLMs locally with one command. The cleanest reference for packaging, quantising, and serving open-weight models.

Self-hosted ChatGPT-style UI for any OpenAI-compatible backend (works with Ollama). Best open-source example of a polished chat interface with RAG built in.

Pure C/C++ inference of Llama models on CPU. The most influential project in the local-LLM movement — study it to actually understand how transformers run.

Production vector database written in Rust. Read it to learn how HNSW indexing, payload filtering, and high-throughput vector search actually work.

One-click deployable Next.js ChatGPT UI supporting OpenAI, Claude, Gemini, and local models. Battle-tested chat UX patterns you can copy directly.

The original framework for building LLM-powered agents and chains. Even if you don't use it, the codebase is a great map of the agent-design space.

Multi-agent framework where each agent has a role, tools, and goals. Cleaner abstractions than LangChain for orchestrating a team of LLMs to complete tasks.

Microsoft's framework for conversable, customisable, and autonomous multi-agent applications. Read it to learn group-chat coordination patterns between LLMs.

Open-source workflow automation with first-class AI nodes. Self-hosted Zapier alternative — perfect for visually wiring LLMs to your real business systems.

Lightweight Python framework for building memory-aware, tool-using AI agents. Cleaner DX than LangChain when you just need an agent that does the thing.

Anthropic's reference SDK for the Model Context Protocol. The cleanest path to expose your app's tools to Claude Desktop, Cursor, and Windsurf.

Not a library — a registry of copy-paste components built on Radix + Tailwind. The single biggest shift in React component distribution in the last 3 years.

The data-fetching library most modern React apps actually use. Read its source to understand cache invalidation, suspense integration, and request dedupe.

Unstyled, accessible React primitives. Reference implementation for every popover, dialog, menu, and combobox you've ever wanted to build correctly.

Performant form library that minimises re-renders. Study it for ref-based state management and how to build a tiny, fast library with zero deps.

Small, fast, and scalable state management. The entire core is < 300 lines — required reading if you want to actually understand React state, not just use it.

The framework for universal React applications. The whole modern RN ecosystem rides on this — study modules, routers, and config plugins to ship faster.

60fps animations on the UI thread. The single most copied animation library in React Native — read it to learn how to bridge JS and native efficiently.

Universal styling system for React Native + web. Production-grade compiler that shows how to optimise styled components at build time across platforms.

The de-facto navigation library for React Native. Read it to learn navigator composition, screen lifecycle, and deep linking the way Meta intended.

Tailwind CSS for React Native via Babel + JSI. Cleanest implementation of utility-first styling on mobile — and the bridge that lets web devs ship native fast.

Curated reading list documenting patterns of scalable, reliable, and performant large-scale systems — articles by prominent engineers plus battle-tested case studies. The single best resource if you're prepping for system-design interviews or actually designing one.

Community-maintained index of freely available programming books, courses, podcasts, and interactive tutorials — organised by language and subject. The largest learn-to-code resource directory on GitHub.

Curated index of Dan Luu's most-read essays on systems engineering, debugging at scale, hiring, and how big tech companies actually work. Pure signal — every link is worth your hour.

Hand-picked collection of resources to learn and review the mathematics behind machine learning — linear algebra, calculus, probability, optimisation, and the intuition you actually need for backprop.

Massive collection of guides to build your own Git, OS, web server, programming language, blockchain, neural network, and more — from scratch.

How to design large-scale systems — prep for system-design interviews and real architecture decisions. The single most-starred learning repo in software.

Interactive roadmaps for frontend, backend, DevOps, AI/ML, Go, React, and 30+ other paths. The clearest map for anyone choosing what to learn next.

Open-source curriculum and platform for learning to code. Study both the lessons AND the codebase — it's one of the largest TypeScript monorepos in production.

Hand-curated short JavaScript, React, Python and Node snippets you can read and absorb in under 30 seconds each. Great for ambient learning.

All major algorithms implemented in dozens of languages (Go, TS, Python, Rust). Best place to compare how the same algorithm reads across paradigms.

Official Next.js bundle analysis plugin. The first tool to reach for when your Next.js app is shipping too much JavaScript to the browser.

Google's automated tool for improving web page quality (perf, SEO, a11y, PWA). The standard every Core Web Vitals discussion is measured against.

Modern load-testing tool that writes test scripts in JavaScript and runs them in Go for performance. Required for API perf testing — pairs with Grafana for results.

Next-generation frontend tooling — instant dev server + Rollup-based prod builds. Study it to understand modern bundling, HMR, and ESM-first dev workflows.

Modern HTTP benchmarking tool capable of generating significant load from a single machine. The tiny C codebase teaches event loops + epoll perfectly.

Google's pprof tool for visualising and analysing CPU/memory profiles. The Go community's default profiler — built right into the std library net/http/pprof.