Developer guides & tutorials
Practical explanations on tools every developer reaches for: JWT decoding, JSON formatting, regex patterns, timestamp conversion, UUID generation, cron expressions, HTTP status codes, and more.
.gitignore Guide: Syntax, Examples, and Patterns for Every Project
Learn how .gitignore works, the pattern syntax, common patterns for Node.js, Python, Java, Go, and macOS, and how to fix files already tracked by git.
HMAC Explained: How to Sign API Requests and Verify Webhook Signatures
Learn what HMAC is, how HMAC-SHA256 works, how to sign HTTP requests with a secret key, and how to verify webhook signatures from services like Stripe and GitHub.
Mock Data Generation: Strategies, Tools, and Best Practices for Testing
Learn how to generate realistic fake data for development and testing: names, emails, dates, UUIDs, addresses, and structured records — without using real user data.
IP Subnet Calculator: CIDR Notation, Subnet Masks, and Network Ranges Explained
Learn how IP subnetting works, how to read CIDR notation, calculate usable host ranges, and why subnetting matters for VPC design, firewalls, and network architecture.
TOTP Explained: How Time-Based One-Time Passwords Work
Understand how TOTP (Time-Based One-Time Passwords) generate 6-digit 2FA codes, the cryptography behind them, how to implement TOTP, and how to generate test codes online.
Docker Compose Guide: Syntax, Examples, and Common Patterns
Learn Docker Compose file syntax field by field. Covers services, networks, volumes, environment variables, health checks, and real-world multi-container patterns.
How to Format and Beautify SQL Queries Online
Format messy SQL into readable, indented queries instantly in the browser. Learn SQL formatting conventions, when to use uppercase keywords, and how formatting helps catch bugs.
How to Browse and Query MongoDB Online Without Installing a Client
Connect to a MongoDB database, browse collections, run queries, and inspect documents directly in your browser. Learn the basics of NoSQL document querying.
How to Test a REST API Online Without Postman
Learn how to send API requests, inspect responses, set headers, use authentication tokens, and debug REST endpoints directly in your browser — no desktop install required.
Password Manager for Developers: Secure Storage Without a SaaS Subscription
Learn how developer-focused password managers work, why browser-based encrypted vaults are useful for local credential storage, and how to protect secrets without leaking them.
HTTP Status Codes Explained: A Developer's Reference
Complete guide to HTTP status codes — 1xx, 2xx, 3xx, 4xx, and 5xx — with explanations, common causes, and how to fix the ones you will encounter most as a developer.
Unix Timestamp to Date: Converter, Format Guide, and Common Pitfalls
Learn what Unix timestamps are, how to convert them to human-readable dates in JavaScript, Python, and SQL, and how to avoid the most common timestamp bugs.
Cron Expression Syntax: Complete Guide with Examples
Learn cron expression syntax field by field with practical examples. Covers standard 5-field cron, extended 6-field formats, special strings, and common patterns for scheduling jobs.
UUID Guide: What They Are, Version Differences, and How to Generate Them
Learn what UUIDs are, the difference between UUID v1, v4, and v7, when to use each, and how to generate UUIDs instantly online without any library.
Base64 Encoding Explained: How It Works and When to Use It
Understand what Base64 encoding is, how it converts binary data to text, common use cases in web development, and how to encode or decode Base64 instantly online.
Regex Lookahead and Lookbehind: Practical Examples
Master regex lookahead and lookbehind assertions with real-world examples. Test patterns in your browser and learn when to use each type of zero-width assertion.
How to Format JSON Online: Beautify, Validate & Minify
Format messy JSON into readable, indented output instantly in the browser. Learn JSON formatting best practices, common errors, and how to minify JSON for production.
How to Decode a JWT Token Online
Learn what a JSON Web Token (JWT) is, how to read its header and payload, and how to decode one instantly in the browser without installing anything.