Developer guides
Practical explanations of the formats and syntax behind our tools — what goes wrong, why, and how to fix it. The examples are tested, and each guide links to the tools it covers.
Common JSON Syntax Errors and How to Fix Them
Trailing commas, single quotes, comments, unescaped characters and other reasons JSON fails to parse, with the error each one produces and the fix.
How JSON Web Tokens Work: Claims, Signatures and Common Mistakes
What is inside a JWT, how the signature is checked, which claims matter and the mistakes that make tokens insecure.
YAML Pitfalls: Indentation, Implicit Types and Multi-line Strings
The YAML mistakes that break configuration files: tabs, inconsistent indentation, values that change type, and block scalars.
Base64 Encoding Explained: Padding, Base64URL and When to Use It
How Base64 turns bytes into text, why it adds padding and a third to the size, how Base64URL differs, and why it is not encryption.
JavaScript Regular Expressions: A Practical Cheat Sheet
Character classes, quantifiers, groups, lookarounds and flags in JavaScript regex, with tested patterns for everyday tasks.
Cron Syntax Explained, With Examples
The five cron fields, ranges, steps and lists, the day-of-month and day-of-week rule, and ready-made schedules you can copy.