Developer Articles
Hands-on articles on developer tools, implementation notes, technical deep dives, and everyday debugging and data conversion workflows.
curl Options Cheat Sheet: What -X, -H and -d Actually Do
A reference for the curl options you meet in real API work: why -d already implies POST, how -d differs from --data-raw, the @ prefix that silently reads a file, single vs double quotes, and why -k and -L deserve more caution than they usually get.
Converting Between JSON Schema and Zod: How required Maps to .optional()
Inside a two-way converter that turns JSON Schema into a Zod schema and Zod code back into JSON Schema. Covers the inverted defaults between required and .optional(), the constraint mapping table, and how the Zod side is parsed without executing any code.
SQL Clause Order Reference: Why WHERE Can't See Your SELECT Alias
The order you write SQL clauses is not the order the database runs them. A reference for the logical execution order (FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY → LIMIT), why aliases fail in WHERE, when to use WHERE vs HAVING, and the MySQL/PostgreSQL differences that bite.
Unified Diff Format Reference: Reading @@ Hunks in git diff Output
How to read the unified diff format git produces: what the four numbers in @@ -12,7 +12,9 @@ mean, why a one-character edit shows as a whole-line replacement, the whitespace and line-ending traps, \ No newline at end of file, combined @@@ diffs on merges, and rename detection via similarity index.
UTC to JST Reference: The 9-Hour Offset, Cheat Sheet & Timezone Pitfalls
Convert between UTC and JST (Japan Standard Time) with a cheat sheet. Covers what Z and +09:00 mean in ISO 8601, when JavaScript date parsing silently shifts by 9 hours, MySQL/PostgreSQL timezone behavior, and why GitHub Actions cron always runs in UTC.
CREATE TABLE Reference: MySQL vs PostgreSQL vs SQLite Types & Constraints
A cross-database CREATE TABLE (DDL) reference with cheat sheets for data types, auto-increment keys (AUTO_INCREMENT / IDENTITY / rowid), foreign key ON DELETE behavior, and the CHECK constraint that MySQL silently ignores.
How CREATE TABLE Generation From a Visual Table Design Works | DDL Builder
A look inside DDL Builder, which turns a visually designed table into CREATE TABLE statements and an ER diagram. Covers the MySQL/PostgreSQL/SQLite type-mapping rules and the column-inference algorithm used for JSON samples.
GitHub Actions needs Design Patterns: Speed Up CI, Avoid the Anti-Patterns
A pattern reference for GitHub Actions job dependencies (needs). Covers diamond-shaped fan-out, concurrency cancellation, fail-fast tradeoffs, matrix-plus-needs gotchas, and reusable workflows, with copy-paste YAML examples.
SQL JOIN Types: Complete Reference to INNER, LEFT, RIGHT & FULL
A reference for SQL JOIN types (INNER/LEFT/RIGHT/FULL/CROSS/SELF) with a cheat sheet and row-count walkthroughs. Covers why one-to-many joins duplicate rows, the WHERE-vs-ON NULL trap, and how to write multi-table joins.
Case Converter: camelCase, snake_case & kebab-case — 9 Styles at Once
Convert identifiers between camelCase, PascalCase, snake_case, CONSTANT_CASE, kebab-case and more — all nine styles side by side. Handles acronym runs like HTTPServer, digits, and bulk multi-line conversion.
LLM API Cost Calculator: Compare Claude, GPT & Gemini Pricing Side by Side
Paste a prompt, set the expected output tokens, and compare per-request API costs across Claude, GPT and Gemini models. Covers input/output pricing structure, auto-updated price tables, and estimate limits.
AGENTS.md, CLAUDE.md, Cursor Rules: One Source of Truth for AI Coding Agents
Every AI coding agent wants its own rules file. Compare AGENTS.md, CLAUDE.md, .cursor/rules, copilot-instructions.md and more — what to write, a copy-paste template, and how to stop them drifting apart.
Mermaid ER Diagram Syntax Reference: Relationship Symbols & Real Examples
Complete reference for Mermaid erDiagram syntax: crow's foot cardinality cheat sheet, one-to-many vs many-to-many, attributes with PK/FK, and a full e-commerce example.
AI Rules Generator: AGENTS.md, CLAUDE.md & Cursor Rules from One Form
Generate rules files for Claude Code, Cursor, GitHub Copilot, Windsurf and Gemini CLI in one shot. Covers the AGENTS.md standard, per-tool file formats, and why a single source of truth prevents rule drift.
LLM Token Counter: Check Claude, GPT & Gemini Token Counts in Your Browser
Paste text and compare token counts for Claude, GPT and Gemini side by side. Covers token basics, why tokenizers differ per model, why non-English text costs more tokens, and the limits of estimates.
IP/CIDR Subnet Calculator: Network, Broadcast & Mask at a Glance
How to calculate the network address, broadcast address, usable hosts, subnet mask and wildcard mask from CIDR notation like 192.168.1.10/24 — with a prefix-length cheat sheet.
Encoding vs Hashing vs Encryption: The Difference and When to Use Each
Base64 encoding, SHA-256 hashing and encryption are constantly confused, yet serve completely different purposes. A comparison table, concrete examples, and the right choice for each use case.
How to Convert HEX, RGB, and HSL Colors and Check Contrast
Convert CSS color formats, adjust colors with HSL, and check foreground/background contrast for readable UI design.
How to Read a QR Code from an Image and Check the URL Before Opening It
Decode QR codes from images or screenshots, verify campaign links before printing, and inspect suspicious QR URLs safely.
How to Count Characters and Clean Text for Docs, Forms, and Code Snippets
Use character counts, line counts, whitespace cleanup, and HTML escaping to prepare text for documentation, metadata, forms, and development workflows.
How to Convert Milliseconds, Seconds, Minutes, and Hours for Timeouts and TTLs
Convert time units for API timeouts, cache TTLs, retry delays, polling intervals, and monitoring settings without mixing up milliseconds and seconds.
How to Convert URL Parameters to JSON for UTM and API Debugging
Turn long query strings into readable JSON so you can review UTM tags, API filters, duplicated keys, and encoded values more easily—with concrete examples.
How to URL Encode and Decode Strings for APIs and Query Parameters
Learn what percent encoding means, when to encode URLs, and how to inspect encoded query strings safely during API and tracking-link debugging.
How to Build SELECT and JOIN Queries Visually with a SQL Builder
Assemble SELECT, WHERE and JOIN clauses in your browser with a visual SQL builder. Useful for learning SQL, extracting data, and drafting queries before review.
CSV and JSON Conversion: Choosing the Right Format for APIs and Data Migration
Learn how to convert between CSV and JSON safely, including headers, delimiters, value types, nested data, and practical workflow tips.
JSON Formatting and Validation: How to Read API Responses Safely
Learn how to format JSON, catch syntax errors, inspect value types, and turn API responses into types, schemas, or documentation.
Create Infrastructure Diagrams in Your Browser: Auto-Generate Diagrams from Code
Use our Mermaid.js-based infrastructure diagram builder to visualize cloud and network configurations just by defining nodes and connections.
Generate ER Diagrams from SQL DDL: How CREATE TABLE Parsing Works
How the SQL to ER diagram tool parses CREATE TABLE DDL into a Mermaid ER diagram — the PRIMARY KEY/FOREIGN KEY extraction rules, how column types are handled, and which DDL patterns aren't supported.
The JSON Ecosystem: Connecting Formatting, Types, Validation, and API Specs
Follow one API response through formatting, TypeScript types, Zod runtime validation, and OpenAPI definitions—with real code at every step—for a clear view of type-safe API development.
JWT Security Deep Dive: Attack Vectors, JWKS, and Production Best Practices
A thorough guide to JWT security — covering the alg:none attack, algorithm confusion, key management with JWKS, token revocation strategies, and a production-ready security checklist.