Documentation and Mission

Tools that respect your privacy

Developer Toolkit is a collection of free, browser-based utilities built for the modern software engineer. We remove every step that isn't necessary.

No Tracking 100% Local Offline Capable

Our Principles

We believe developer tools should be fast, private, and out of your way. These four pillars guide every feature we build.

Privacy first

Every tool runs entirely in your browser. Production payloads, API tokens, JWT secrets, and config files never leave your device. We have no way to see your inputs, and that's the point.

No friction

No sign-up. No paywall. No rate limits on the free tier. You land on a tool page, paste your input, and get output in under 10 seconds. We remove every step that isn't necessary.

Developer quality

Tools handle edge cases that generic utilities miss: BigInt precision loss in JSON, JWT expiry warnings, UUID version differences. Every tool has keyboard shortcuts and works offline after first load.

Sustainably free

The free tier stays free forever. Developer Toolkit is supported by non-intrusive developer-targeted ads from Carbon Ads or EthicalAds. No cookie walls, no paywalls, no data brokering. A future paid REST API tier will let teams use these tools programmatically in CI/CD pipelines.

Available tools

A comprehensive list of all verified utilities currently running in the toolkit.

View latest updates

JSON Formatter & Validator

Format, beautify, validate, and minify JSON. Detects BigInt precision issues, duplicate keys, and JSONC comments.

Base64 Encoder / Decoder

Encode or decode Base64 strings instantly. Supports standard and URL-safe variants.

JWT Decoder

Decode and inspect JWT tokens. View header, payload, and signature without a secret.

UUID / ULID Generator

Generate RFC-4122 UUIDs (v1, v4, v5) and ULIDs instantly.

Unix Timestamp Converter

Convert Unix timestamps to human-readable dates and vice versa.

Regex Tester

Test and debug regular expressions with real-time match highlighting.

URL Encoder / Decoder

Encode or decode URL components and query strings.

Hash Generator

Generate MD5, SHA-1, SHA-256, and SHA-512 hashes from any string.

JSON Diff

Compare two JSON objects side-by-side and highlight differences.

Text / Code Diff

Compare two text blocks and highlight line-by-line differences.

HEX / RGB / HSL Color Converter

Convert colors between HEX, RGB, and HSL formats instantly.

Cron Expression Builder

Build and validate cron expressions with a human-readable description.

JWT Generator & Verifier

Generate and verify JWT tokens with HS256 or RS256 signing.

Number Base Converter

Convert numbers between binary, octal, decimal, and hexadecimal.

Markdown Preview

Write and preview Markdown with live rendering.

Online Notepad

Autosaving plain-text editor with word count, Find & Replace, and .txt download. Nothing leaves your browser.

Word Counter

Real-time words, characters, sentences, paragraphs, reading time, and keyword density analysis.

QR Code Generator

Generate QR codes for URLs, text, WiFi credentials, emails, and vCards. Custom colors, PNG/SVG download.

Password Generator

Generate cryptographically secure passwords and EFF-style passphrases using the Web Crypto API.

Lorem Ipsum Generator

Generate placeholder text by paragraph, sentence, or word count. Classic and authentic Cicero Latin variants.

Image to Base64

Convert PNG, JPG, GIF, WebP, SVG, and BMP to Base64. Output as raw string, CSS background-image, or HTML <img> tag. Drag & drop.

YAML ↔ JSON Converter

Convert YAML to JSON or JSON to YAML with a direction toggle. Powered by js-yaml. Bidirectional and lossless.

JSON ↔ TOON

NEW

Convert JSON to TOON (Token-Oriented Object Notation) to reduce LLM prompt token usage by ~40%. Lossless and bidirectional.

HTML to Markdown

Convert HTML or pasted rich text to GitHub Flavored Markdown. Tables, strikethrough, task lists supported.

SQL Formatter

Format and beautify SQL queries for MySQL, PostgreSQL, SQLite, T-SQL, and Standard SQL. Keyword casing control.

Case Converter

Convert text to camelCase, PascalCase, snake_case, SCREAMING_SNAKE, kebab-case, Title Case, and 3 more formats. All 9 at once.

CSV to JSON Converter

Convert CSV to JSON or JSON to CSV in your browser. Supports custom delimiters, header rows, and dynamic typing.

XML Formatter

Format, beautify, and minify XML online. Validates XML structure and supports custom indentation.

HTTP Status Codes

Complete HTTP status code reference with descriptions. Search and filter all 1xx, 2xx, 3xx, 4xx, and 5xx codes.

CSS Formatter

Format, beautify, and minify CSS code online. Shows byte reduction percentage on minify.

TOML to JSON Converter

Convert TOML to JSON or JSON to TOML. Supports Cargo.toml, pyproject.toml, and Hugo config files. Bidirectional.

JSON Schema Validator

Validate JSON data against a JSON Schema in your browser. See detailed error paths and messages. Supports draft-07 and 2020-12.

Unicode Lookup

Look up Unicode code points, HTML entities, hex values, and UTF-8 bytes for any character or text. Supports emoji.

AI Token Counter

NEW

Count tokens for GPT-4o, GPT-4, GPT-3.5, Claude, and Gemini. See context window usage and estimated API cost.

MCP Config Builder

NEW

Build MCP server configs for Claude Desktop and Claude Code visually. Add presets, set env vars, copy JSON instantly.

Code to Image

NEW

Turn any code snippet into a beautiful screenshot. Pick a theme, font, and background, then download a shareable PNG. Runs fully in your browser.

WCAG Color Contrast Checker

NEW

Check WCAG 2.1 contrast ratios for AA and AAA, normal and large text. Live preview plus accessible color suggestions.

.env ↔ JSON / YAML Converter

NEW

Convert .env files to JSON or YAML and back. Handles comments, quotes, export prefixes, and nested keys. Bidirectional.

CSS Gradient & Box-Shadow Generator

NEW

Generate linear, radial, and conic CSS gradients and layered box-shadows with a live preview. Copy ready-to-use CSS.

SVG Optimizer

NEW

Optimize and minify SVG in your browser. Strip metadata, round precision, and export as SVG, data URI, or Base64. See bytes saved.

Why you can trust it

Privacy is not a setting you toggle. Every guarantee below is a consequence of how the product is built, not a policy we could change or a promise we could break.

Structural privacy

No server processes your input. No database stores your payloads. The guarantee is architectural, not a policy. We have no technical means to see what you paste in.

No accounts, ever

No sign-up, no session tokens, no fingerprinting. Nothing ties your activity to an identity. There is no account in this system and therefore nothing to compromise.

Works offline

Every tool is statically generated and caches on the first visit. Return hours later without a connection and every tool still runs exactly as expected.

Nothing to go down

No backend can fail, no rate limiter can throttle you, and no deploy can break your workflow mid-task. It is a static page served directly from a global CDN.

Questions or feedback?

Found a bug? Have a tool request? Want to collaborate? We've set up direct email routes for all inquiries so you can reach the right person instantly.

Get in touch