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DeveloperToolbox — 100% Free

23+ free online developer tools · Pure frontend · Your data stays on your device

✦ 23 Tools✦ Client-side✦ Zero Upload✦ 中/EN

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100% Free

All tools are free forever. No hidden charges, no premium tiers, no credit card needed.

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Privacy First

Every tool runs in your browser. Zero data leaves your device. No servers, no logs, no tracking.

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Works Offline

Once loaded, tools work without internet. No backend, no API calls, no latency.

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Converters

Transform between formats

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XML ↔ JSON Converter

Convert XML to JSON and JSON to XML. Handles attributes, nested elements, and namespaces.

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YAML ↔ JSON Converter

Convert YAML to JSON and back. Essential for K8s, Docker Compose, CI/CD configs.

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CSV ↔ JSON Converter

Convert CSV spreadsheet data to JSON arrays and back. Handles headers and delimiters.

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TOML ↔ JSON Converter

Convert TOML config files to JSON. Works with Cargo.toml, pyproject.toml.

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Markdown → HTML

Convert Markdown to HTML with live preview. Supports GFM and code blocks.

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Encoders & Decoders

Encode and decode data

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Base64 Encoder / Decoder

Base64 encoding and decoding with UTF-8 support

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URL Encoder / Decoder

URL encoding and decoding for special characters and Unicode

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HTML Entities Encoder / Decoder

Escape and unescape HTML special characters

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Formatters & Validators

Beautify and validate

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JSON Formatter / Validator

Format, minify, and validate JSON data

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XML Formatter / Validator

Format, validate, and minify XML. Catch mismatched tags and escaping issues.

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SQL Formatter

Format SQL queries with multiple dialect support

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.env File Validator

Validate, compare, and analyze .env files across environments

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Design & Reference

Colors, codes, and references

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Color Converter & Tools

Convert between HEX, RGB, HSL. Check contrast and explore palettes.

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Code to Image

Convert code snippets into beautiful shareable images

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HTTP Status Code Reference

Quick reference for all HTTP status codes with descriptions

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Utilities

Inspect and convert values

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JWT Decoder

Decode and inspect JSON Web Tokens. View header, payload, and expiration.

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Timestamp Converter

Unix timestamp to date, auto-detect seconds/milliseconds

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Cron Expression Generator

Visual Cron expression builder with presets and syntax reference

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UUID Generator

Generate UUID v4 in batches

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Regex Tester

Online regex testing with flags and real-time matching

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Number Base Converter

Convert between binary, octal, decimal, and hexadecimal

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SemVer Range Visualizer

Visualize npm/pip/cargo semantic versioning ranges on an interactive timeline

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