Free
SQLite
Open SourceRelational · Database
Self-contained, serverless, embedded SQL database engine.
sqlitesqldatabaseembedded
Browse the complete directory — use filters to narrow down.
Relational · Database
Self-contained, serverless, embedded SQL database engine.
SQL Tools
Interactive SQL tutorial with quizzes for beginners.
Compression & Optimization · Image & Media
Google's browser image compressor with advanced codecs (WebP, AVIF).
SSL & TLS · Security
Deep SSL/TLS server certificate and configuration analysis.
Communities · Documentation & Learning
The largest Q&A community for programmers.
PDF Tools · PDF & Documents
Self-hosted PDF toolbox with 50+ operations, locally run.
Illustrations & Assets · Design & Prototyping
Freepik's library of customizable vector illustrations — recolor, animate and export for products and decks.
Compression & Optimization · Image & Media
Browser GUI for SVGO, optimizing SVG files with previews.
References · Documentation & Learning
The most-starred system design study guide — scalable architectures, trade-offs and exercises, free and open source.
Practice & Challenges · Documentation & Learning
Free, curated interview prep: algorithms study plans, behavioral questions and resume advice by ex-Facebook engineers.
Courses & Tutorials · Documentation & Learning
Free, open-source full-stack web development curriculum.
Cheatsheets · Documentation & Learning
Community-maintained, practical examples for every CLI command.
Other Formats · Data Formats
Official TOML language site with spec, docs and editor support.
JSON · Data Formats
Convert JSON into TypeScript, Zod, GraphQL, Kotlin, Go structs and more.
Typography & Fonts · Design & Prototyping
Visual type-scale calculator — pick a ratio and base size, preview the resulting hierarchy live.
Color Tools
Generate Tailwind CSS color scales from any base color.
Web Analytics · Monitoring & Observability
Simple, self-hostable web analytics you own (trending).
Design Tools · Design & Prototyping
Free open-source SVG illustrations with a live color picker.
Converters · Encoding & Decoding
Browse and search all Unicode characters by block and codepoint.
Uptime & Alerting · Monitoring & Observability
Fancy open-source self-hosted uptime monitoring with status pages.
Converters · Encoding & Decoding
Encode and decode URLs and query strings online.
SQL Tools
In-depth guide to SQL indexing and performance tuning.
Passwords & IDs · Security
Generate UUIDs/GUIDs in bulk, including v4 and v7 versions.
NoSQL · Database
Community-driven Redis fork under the Linux Foundation (trending).