DevToolbox
Developer tools that run in your browser. Nothing you paste is sent to a server, and the tools you have opened keep working offline.
33 tools found
Data & formats
Format, validate, convert and compare data.
JSON to Types & Schema
Generate TypeScript, Zod, Python and JSON Schema from sample JSON.
Timestamp & Cron
Convert Unix timestamps across time zones and read cron expressions with next run times.
Colour Palette & Contrast
Convert colours, build palettes and check WCAG contrast with suggestions.
CSS Unit Converter
Convert px, rem, em, vw and more, convert whole stylesheets and build clamp() sizes.
SQL Formatter
Format or compact SQL for PostgreSQL, MySQL, SQLite and SQL Server.
JSON Formatter & Validator
Format, minify and validate JSON with clear error positions.
Multi-Format Converter
Convert between CSV, JSON, XML and Excel.
Diff Checker
Compare two texts side by side.
API Contract Diff
Compare two JSON responses or schemas by field path and spot breaking changes.
Security & encoding
Tokens, hashes, encodings and passwords.
JWT Decoder & Inspector
Decode and inspect JSON Web Tokens locally.
URL Parser & Encoder
Split a URL into parts, edit its query and compare URL encodings.
.env Checker & Example Generator
Check a .env file and build a safe .env.example without leaking secrets.
Hash & Encoding Workbench
Hash text and encode or decode Base64, URL and more.
Password Generator
Create strong random passwords in your browser.
Text
Generate and shape text.
Mock Data & Test Cases
Realistic test data and boundary values from a schema, as JSON, CSV or SQL.
Lorem Ipsum & Fake Text
Placeholder paragraphs and sample data.
Regex Tester & Pattern Library
Test JavaScript regex live, read an explanation and start from ready-made patterns.
Text-to-Diagram
Write Mermaid and see the diagram live.
Testing
Selectors and test automation helpers.
AI
Evaluate prompts and model answers, and prepare text for AI assistants.
LLM-as-a-Judge
Compare a candidate answer with a reference.
LLM Prompt Tester
Run a prompt and inspect the evaluation.
Error to AI Prompt & Secret Masker
Clean stack traces, mask secrets and prepare text for AI assistants.
AI Output Cleaner
Clean AI-generated Markdown, JSON, SQL and code locally.
Do These Packages Exist?
List the npm and PyPI packages in AI-written code and check each one exists.
Needs network
Code Packer for AI
Turn a project folder into one text for an AI assistant, with secrets masked.
Network
HTTP references, webhooks and disposable inboxes.
Open Graph & Meta Tags
Preview search and share cards and generate meta, Open Graph and Twitter tags.
robots.txt & Sitemap
Generate and validate robots.txt and sitemap.xml, and test what a crawler may fetch.
CORS Error Troubleshooter
Explain a CORS error, its likely causes and the headers a server must send.
HTTP Status Codes
Every status code explained, with a which-code-to-return helper.
Temp Mail
A disposable inbox for testing sign-ups.
Needs network
Webhook Catcher
Get a URL that records the requests sent to it.
Needs network