Resources for working developers
A hand-curated list of 55+ free resources across 9 categories. Code quality, architecture (incl. DDD), security, testing (incl. TDD + Playwright), AI development with LLMs, docs, courses, news, newsletters. Chosen because they're authoritative (the author IS the subject matter), free (no paywall on the primary content), and durable (they've survived > 3 years and show active maintenance).
Everything here is a link — we don't scrape or re-publish anyone else's writing. If you find a resource that belongs on this list, open an issue onGitHub.
Code quality & best practices
Patterns, principles, and habits that compound over a career. Not language-specific — the ideas transfer.
Google Engineering Practices
Google's open guide to code reviews, change authorship, and reviewer expectations. The small-CL doctrine alone will level up every team that reads it.
google.github.io
Refactoring Guru
Design patterns and refactoring techniques explained with vivid diagrams and runnable examples across many languages.
refactoring.guru
You Don't Know JS Yet (book series, free online)
Kyle Simpson's deep JavaScript series. Free to read in full on GitHub. Essential for anyone who ships JS and wants to stop guessing.
github.com/getify
Martin Fowler — Bliki
Short, pointed essays on refactoring, continuous integration, enterprise patterns, and the discipline of writing software. Timeless.
martinfowler.com
Clean Code (summary)
Robert C. Martin's canonical rules for readable code. Not everyone agrees with every chapter, but the vocabulary it gives teams is worth the read.
github.com/JuanCrg90
Architecture & system design
How to make systems that scale with your team and traffic — before you need to.
The Twelve-Factor App
The 12 constraints that make a web app operable in a modern cloud deployment. Short, specific, foundational.
12factor.net
microservices.io
Chris Richardson's pattern catalogue for microservices — when they help, when they hurt, and the exact tradeoffs for each pattern.
microservices.io
The System Design Primer
Donne Martin's open resource for learning how to design large systems. Interview-oriented but useful for anyone building anything.
github.com/donnemartin
Clean Architecture (Uncle Bob) — summary
The "layers that depend inward" pattern made famous by Robert C. Martin. A good lens for keeping business logic decoupled from frameworks.
cleancoder.com
Designing Data-Intensive Applications (book outline)
Martin Kleppmann's book is the modern canonical reference for distributed systems. The author also hosts open talks + the chapter outlines on his site.
dataintensive.net
Domain-Driven Design — reference (Eric Evans)
The free 50-page distillation of the original DDD book. Ubiquitous language, bounded contexts, aggregates — the vocabulary every architect uses. Read this once; refer back for the next decade.
domainlanguage.com
DDD Starter Modelling Process (Nick Tune)
A practical, step-by-step guide to applying DDD to a new project. Event storming → context mapping → aggregate design, with worked examples. The modern on-ramp if the Evans book feels abstract.
github.com/ddd-crew
Microsoft — DDD-oriented microservice design
Microsoft's architecture guide for applying DDD + CQRS + event sourcing in .NET-shaped services, but the patterns translate to any stack. Especially useful on tactical patterns (entities, value objects, repositories).
learn.microsoft.com
Security
Writing secure code is a skill, not a trait. These resources are hands-on — expect to find real attacks, real defences, and labs you can run.
OWASP Top 10
The baseline every web developer should know. Pair with the OWASP Cheat Sheet series for actionable mitigations per language / framework.
owasp.org
OWASP Cheat Sheet Series
Per-topic quick references: authentication, XSS, SQL injection, cryptography, session management. Deep, free, maintained by practitioners.
owasp.org
PortSwigger Web Security Academy
From the makers of Burp Suite — a free lab-based course on web app security. The gold standard; completing the labs makes you measurably better.
portswigger.net
web.dev Security
Google's practical security guides for web developers: CSP, CORS, cookies, HTTPS, Trusted Types. Short reads, high signal.
web.dev
HackerOne Hacker101
Free security training by HackerOne. Oriented at bug bounty hunters but the lessons translate directly to defensive coding.
hacker101.com
Testing
The craft of writing tests you want to run, not tests you want to delete. Pragmatic over dogmatic.
Kent C. Dodds — Testing JavaScript
Blog posts, free egghead videos, and the "trophy" testing model. Opinionated in a useful way.
kentcdodds.com
Martin Fowler — Testing taxonomy
Unit vs integration vs contract vs end-to-end — Fowler's essays clarified the vocabulary the industry now uses. Useful before every architecture decision.
martinfowler.com
Google Testing Blog
Internal Google testing patterns made public: test-sizing, hermetic tests, flaky-test triage. Years of lessons from a huge codebase.
testing.googleblog.com
Test-Driven Development by Example (Kent Beck — book summary)
The original red-green-refactor loop, by the author who coined it. Even if you don't practice strict TDD, the thinking-in-small-steps discipline it teaches makes everything else easier.
tidyfirst.substack.com
Playwright — official docs
The modern E2E / browser-automation framework. First-class TypeScript, auto-wait, multi-browser, hermetic fixtures. The getting-started + the testing-strategy pages are mandatory before writing your first spec.
playwright.dev
Vitest docs — unit + integration patterns
The vite-native unit test runner. Fast, Jest-compatible API, great TypeScript ergonomics. The "mocking" and "test context" pages cover the integration patterns most tutorials skip.
vitest.dev
The Practical Test Pyramid (Ham Vocke / Martin Fowler)
The pyramid you were probably taught, drawn properly: lots of unit tests, fewer integration, few E2E, with concrete code examples for each layer. The reference for scoping a test strategy.
martinfowler.com
Free courses & structured learning
Full curricula, no paywall, no credit card. Suitable for self-study or as pair-programming source material.
freeCodeCamp
Full certifications in web dev, data science, and more. Free, project-based, with built-in community.
freecodecamp.org
The Odin Project
Full-stack curriculum (Ruby or JavaScript tracks). Project-first; the community is excellent.
theodinproject.com
CS50 (Harvard)
Harvard's introduction to computer science, free online. Lectures, problem sets, and a strong finishing project. Rigorous foundations.
cs50.harvard.edu
Full Stack Open (University of Helsinki)
Modern full-stack with React, Node, TypeScript, GraphQL, testing, deployment. One of the best free university-grade courses available.
fullstackopen.com
MIT OpenCourseWare — EECS
The actual MIT computer science syllabus — courses, problem sets, exams. No credit, no fee, no filler.
ocw.mit.edu
Coursera — Computer Science catalog (free audit)
University courses from Stanford, Princeton, Michigan, Google and others. The content is free to audit — only the certificate costs. "Audit" means every video, every reading, every quiz.
coursera.org
edX — Computer Science (free audit)
edX hosts MIT, Harvard and Berkeley CS courses with the same free-to-audit model. The "Verified Certificate" is optional; the learning is not.
edx.org
Anthropic Academy — build with Claude
Interactive courses on prompt engineering, agent building, tool use, and the Model Context Protocol. Free, hands-on, maintained by the team shipping the models.
anthropic.skilljar.com
Anthropic cookbook — code examples
The repo of worked examples for every major Claude capability (tool use, vision, RAG, agents, PDF handling, extended thinking). Clone it, run it, modify it — it's the fastest route from docs to working code.
github.com/anthropics
AI development & engineering with LLMs
The LLM space moves faster than any blog can cover. These are the authors + resources whose signal-to-noise ratio has held up through the hype cycle.
Anthropic — building effective agents (engineering blog)
The clearest working-engineer post on when to reach for an agent vs. a plain prompt, and the patterns (prompt chaining, routing, orchestrator-workers, evaluator-optimizer) that compose cleanly. Required reading before building anything bigger than a chat loop.
anthropic.com
Simon Willison — LLM-focused blog
The single highest-signal LLM blog on the web. Daily link-blogging across every major release, every security disclosure, every usable technique. If you only subscribe to one LLM-focused RSS, make it this one.
simonwillison.net
Prompt Engineering Guide (DAIR.AI)
Community-maintained guide covering zero-shot, few-shot, chain-of-thought, ReAct, Tree-of-Thought and everything in between. Each technique has a worked example you can paste into any model.
promptingguide.ai
OWASP Top 10 for LLM Applications
The security-specific threats LLM apps face: prompt injection, insecure output handling, training data poisoning, supply chain, excessive agency. Treat this as mandatory before shipping any LLM-touching feature.
owasp.org
Chip Huyen — ML engineering blog
Production-oriented ML + LLM content from the author of "Designing Machine Learning Systems". Especially strong on evaluation, deployment, and the costs no tutorial mentions.
huyenchip.com
Hamel Husain — LLM evaluations in depth
Pragmatic, worked write-ups on building evals that actually catch regressions. If "we need better evals" sounds vague, this is where it becomes concrete.
hamel.dev
News & community
Where developers go to see what's shipping today. Set a 15-minute daily cap on these; they'll eat your afternoon otherwise.
Hacker News
The front page of what engineering circles are reading today. The comments are usually more valuable than the links.
news.ycombinator.com
Lobsters
Invitation-only variant of HN with a stricter on-topic policy — higher signal, lower volume, focused on computing.
lobste.rs
dev.to
A friendlier Medium for developers. Mixed quality but the community is active and the comment culture is kind.
dev.to
Smashing Magazine
Front-end-focused, long-form, well-edited. Especially strong on CSS, accessibility, and design-system patterns.
smashingmagazine.com
The Changelog podcast
Weekly interviews with open-source maintainers. The best way to find out which tools are actually being adopted vs. which are only being announced.
changelog.com