Free
Let's Debug
Open SourceSSL & TLS · Security
Diagnose why Let's Encrypt certificate issuance fails for a domain.
letsencryptssldiagnostics
Browse the complete directory — use filters to narrow down.
SSL & TLS · Security
Diagnose why Let's Encrypt certificate issuance fails for a domain.
Models & LLM APIs · AI for Developers
Open-source LLM gateway: one API for 100+ providers.
Models & LLM APIs · AI for Developers
Meta's open-weight LLM family with downloadable weights.
Email · API Tools
Self-hosted email testing tool with a web UI, catches local mail.
Relational · Database
Community-developed MySQL fork with a permissive license.
Markdown · PDF & Documents
Free reference and tutorial for Markdown syntax.
Design Systems · Design & Prototyping
Google's open-source design system with guidelines and tokens.
MCP · AI for Developers
The open standard connecting AI models to tools and data sources.
References · Documentation & Learning
The definitive reference for HTML, CSS and JavaScript, by Mozilla.
NoSQL · Database
The classic, simple distributed memory object cache.
Other Formats · Data Formats
Efficient binary serialization format, JSON-like but compact.
Favicons & Social Images · Image & Media
Preview and generate Open Graph and social meta tags.
Stock & Placeholders · Image & Media
Free stock video, music tracks, sound effects and templates under the Mixkit license — no attribution needed.
SQL Tools
Free, structured SQL tutorial from basics to advanced analytics.
SSL & TLS · Security
Generate recommended TLS configurations for many servers.
Queues & Streaming · Database
Lightweight, high-performance messaging and microservices bus.
Generators · CSS Tools
Generate soft-UI (neumorphism) shadow CSS.
Web Servers & Proxies · DevOps
DigitalOcean's visual generator for performant Nginx configs.
Package Managers · Development Environment
Default Node.js package manager and the world's largest package registry.
Authentication · API Tools
Official resource for the OAuth 2.0 authorization framework.
Cheatsheets & Learning · Git & Version Control
Plain-language recipes for recovering from common Git mistakes.
Illustrations & Assets · Design & Prototyping
Hand-drawn character illustration library (CC0) — mix faces, poses and outfits into millions of combos.
Search Engines · Database
Community-driven, open-source fork of Elasticsearch and Kibana.
APM & Tracing · Monitoring & Observability
Vendor-neutral standard for traces, metrics and logs instrumentation.