Guides & Tutorials
Practical, privacy-first developer guides — using free tools that run entirely in your browser.
CSS Custom Properties: A Practical Guide to Design Tokens
What CSS custom properties (CSS variables) are, how to structure a design token system with them, and how to generate a full color scale — all in your browser.
Regular Expressions Quick Reference: Common Patterns Explained
The most useful regex patterns for developers — email, URL, date, number, word boundaries — explained with examples and a free in-browser tester.
JSON to Go, Rust, TypeScript: Code Generation Tools for Any Language
Stop writing boilerplate struct definitions by hand — paste a JSON sample and generate typed structs for Go, Rust, TypeScript, and PHP instantly in your browser.
What to Put in .gitignore (and Why)
Which files and directories to exclude from version control for Node, Python, Go, Rust, and more — plus the .gitignore pattern syntax every developer should know.
Why Client-Side Tools Are Safer: Free, Private, No Upload
Most online dev tools upload your data to a server. Client-side tools run entirely in your browser, so your JSON, tokens, and secrets never leave your device — here's why that matters and how to tell the difference.
Pure CSS UI: Buttons, Loaders, and Animations Without JavaScript
Build buttons, loading spinners, and keyframe animations with CSS alone — no JavaScript, no images — for lighter pages and fewer dependencies, with free generators for each.
BMR, TDEE, and Body Fat: The Numbers Behind Your Calorie Goals
How BMR, TDEE, and body-fat percentage relate — what each number means, the formulas behind them, and how to use them to plan a cut or a bulk. All computed in your browser.
How Mortgage Payments Work: PITI, Interest, and PMI Explained
What makes up a monthly mortgage payment — principal, interest, taxes, insurance, and PMI — plus the amortization formula and how to estimate yours in your browser.
URL Encoding and Decoding, Explained
What percent-encoding is, which characters need escaping, encodeURI vs encodeURIComponent, and how to encode or decode URLs safely in your browser.
MD5 vs SHA-256: Which Hash Should You Use?
MD5, SHA-1 and SHA-256 compared — what hashing is, why MD5 and SHA-1 are broken for security, when each is still fine, and how HMAC differs. With free in-browser hash tools.
UUID vs ULID vs Nano ID: Choosing an ID Format
How UUID, ULID and Nano ID differ — randomness, sortability, length, and URL-friendliness — and which to pick for database keys, public IDs, and short links.
How to Format and Validate JSON Online
Format, validate, minify, and convert JSON entirely in your browser — plus the privacy reason you shouldn't upload sensitive payloads to a server.
How to Decode a JWT Safely in Your Browser
What's inside a JWT, the difference between decoding and verifying, and how to read a token's claims without sending a live credential to someone else's server.
Base64 Encoding and Decoding, Explained
What Base64 actually is, when to use it, why it is NOT encryption, the 33% size overhead, and Base64 vs Base64URL — with a free in-browser encoder/decoder.