Developer Learning Guides
Practical guides on regex, CSS, JSON, and more — with interactive examples.
Regex Basics: A Complete Beginner's Guide
Learn regular expressions from scratch. Understand patterns, metacharacters, and how to write your first regex.
Regex Special Characters: Complete Reference
Master every regex metacharacter and special character with examples and interactive tests.
Regex Groups and Captures Explained
Learn how to use capturing groups, non-capturing groups, and named groups to extract data with regex.
Regex Quantifiers: Complete Guide
Master greedy, lazy, and possessive quantifiers in regular expressions with practical examples.
CSS Selectors: The Complete Guide
Learn every type of CSS selector — from basic to advanced — with examples and specificity explanations.
CSS Specificity: Why Your Styles Aren't Applying
Understand how CSS specificity works, how to calculate it, and how to avoid the !important trap.
JSONPath Syntax: Query JSON Like XPath
Learn JSONPath syntax to query, filter, and extract data from nested JSON structures.
Unix Timestamps Explained
Everything you need to know about Unix time — what it is, how it works, and common pitfalls.
Base64 Encoding Explained
Understand what Base64 is, how it works, when to use it, and when not to.
JWT Structure and How It Works
Understand JSON Web Tokens: their structure, how to decode them, and when to use (and not use) them.