YAML Multiline Strings
Choose between | and >, control trailing newlines and fix indentation.
Learning library
Developer Guides
Focused explanations and testable examples for the developer task in front of you.
Topic
YAML & Config
YAML Comments
See when # is a comment, literal text or part of a block scalar.
YAML vs YML: Is There Any Difference?
Understand why .yaml and .yml use the same syntax and choose a consistent extension.
YAML Lists and Arrays: Syntax and Examples
Build YAML sequences, lists of objects and nested arrays with correct indentation.
YAML Anchors and Aliases Explained
Reuse YAML nodes with anchors and aliases while keeping configuration readable.
Topic
Regex & Text
Regex Cheat Sheet
Reference common regex tokens and test them in the shared Regex Lab.
Regex Whitespace
Choose the right pattern for spaces, tabs, newlines or trimming.
Regex for Numbers
Build patterns for digits, signed values and decimals, then test real input.
JavaScript String Length
Compare .length, code points, graphemes and UTF-8 bytes on real strings.
Regex Groups, Capture Groups and Backreferences
Group alternatives, capture matched text and reuse captures with backreferences.
Regex Lookahead and Lookbehind Explained
Check surrounding regex context without consuming it in the match.
Topic
JSON & Schema
JSON Schema Arrays
Define array items, validate objects and diagnose item-level failures.
JSON Schema Pattern
Test a regex, escape it for JSON and validate it inside a schema.
JSON Schema enum: Allowed Values and Examples
Restrict values with enum, compare const and test invalid cases.
JSON Schema additionalProperties Explained
Allow, reject or validate object properties not named explicitly.
JSON Schema oneOf vs anyOf vs allOf
Choose exactly one, one or more, or every schema branch.
Unexpected End of JSON Input: Causes and How to Fix It
Find empty, truncated or unfinished JSON without guessing missing data.
JSON Comments: Are Comments Allowed in JSON?
Distinguish strict JSON from JSONC, JSON5 and comment-like data properties.
JSON Escape Characters Explained: Quotes, Backslashes, Newlines, and Unicode
Decode JSON quotes, backslashes, control escapes, Unicode and nested serialization layers.
Topic
Data Formats
What Is a CSV File? Format, Structure, Examples, and Common Pitfalls
Understand rows, fields, headers, quoting and CSV dialects.
JSON vs CSV: Differences, Use Cases, and Which Format to Choose
Compare hierarchical JSON with flat tabular CSV using one dataset.
CSV vs Excel (XLSX): What’s the Difference?
Choose plain-text CSV or a feature-rich XLSX workbook.
XML vs JSON: Differences, Examples, and When to Use Each
Compare syntax, data models, types, ordering and the use cases each format serves best.
XML Comments: Syntax, Rules, and Examples
Write valid <!-- comments --> and avoid double-hyphen and nesting errors.
XML Attributes vs Elements: Differences and When to Use Each
Choose between attributes and child elements based on structure, repetition and meaning.
XML Arrays Explained: Repeated Elements, Lists, and JSON Mapping
Map repeated XML elements and list containers to predictable JSON arrays.
Markdown Table Syntax and Examples
Create readable tables with headers, delimiter rows, alignment and portable cell content.
How to Escape Pipes in Markdown Tables
Prevent literal | characters in code, regex and text from creating accidental table columns.
Topic
Systems & DevOps
Topic
Security & Certificates
What Is a Certificate Signing Request (CSR)?
Understand what a PKCS#10 CSR contains and how it relates to a certificate and private key.
JWT Structure: Header, Payload and Signature
Separate the header, payload and signature, and see what Base64URL decoding does not prove.
JWT Claims Explained: exp, iat and nbf
Interpret expiration, issued-at and not-before timestamps without mixing their roles.
Decode vs Verify JWT: What’s the Difference?
Understand why readable JWT claims remain untrusted until cryptographic verification succeeds.
Topic
Web & Encoding
URL Encoding Spaces: %20 vs + Explained
Choose %20, + or %2B correctly in URL paths and form-style query values.
XML Escape Characters: Special Characters, Entities, and Examples
Escape &, <, quotes and apostrophes with entities or numeric character references.
XML Encoding Explained: UTF-8, UTF-16, and the XML Declaration
Understand UTF-8, UTF-16, BOM detection and the XML encoding declaration.
Base64 Images and Data URIs Explained
Build valid image Data URIs for HTML and CSS and understand their size and caching trade-offs.
Practice with tools
Move from explanation to a real result
Every guide connects a focused concept to the existing browser-based tool that can test it.