100 Free Developer Tools That Run in Your Browser

DevKit is a collection of 100 free developer tools that process entirely in your browser. No signup, no backend, no data leaving your device — fast, clean tools for everyday dev work across 8 categories. Here's what's available.

Privacy-first: Every tool runs 100% client-side. Your API keys, JWTs, wallet addresses, and sensitive configs never touch a server.
Browse All 100 Tools →

Format & Validate

JSON Formatter & Validator →
Format, validate, and minify JSON with real-time error detection
SQL Formatter →
Format SQL queries with keyword uppercasing and indentation
YAML Formatter & Validator →
Format and validate YAML; detect syntax errors; convert to JSON
Markdown Preview →
Write Markdown with live rendered HTML preview side by side
HTML Formatter & Minifier →
Format, beautify, and minify HTML
CSS Formatter & Minifier →
Format and minify CSS stylesheets

Encode & Decode

Base64 Encode / Decode →
Encode text to Base64 or decode Base64 to text (full UTF-8)
URL Encode / Decode →
Encode/decode URL components; handles special chars and Unicode
JWT Decoder →
Decode JSON Web Tokens; inspect header, payload, expiration
Image to Base64 →
Convert PNG, JPG, SVG, GIF, WebP images to Base64 data URLs
Unicode Inspector →
Character-by-character: code points, UTF-8 bytes, HTML entities

Convert

Timestamp Converter →
Convert Unix timestamps to dates and back; live clock
JSON ↔ CSV Converter →
Convert between JSON arrays and CSV; handles nested objects
cURL to Fetch Converter →
Convert cURL commands to JavaScript fetch() or async/await
JSON to TypeScript Interface →
Convert JSON objects to TypeScript interfaces and types
HTML to JSX Converter →
Convert HTML to valid JSX — class→className, inline styles
Color Converter →
Convert between HEX, RGB, HSL with live color preview

Test & Compare

Regex Tester →
Test regular expressions in real time with match highlighting
Text Diff Checker →
Compare two texts side by side with highlighted diffs
Color Contrast Checker →
WCAG AA and AAA contrast ratio checker for accessibility
Password Strength Checker →
Entropy calculation, pattern detection, time-to-crack estimates
Word & Character Counter →
Count words, characters, sentences, paragraphs, reading time
HTTP Security Headers Analyzer →
Audit HTTP security headers — get A+–F grade + fix snippets

Generate

UUID Generator →
UUID v4 — instant, bulk generate, copy
Hash Generator →
Generate SHA-1, SHA-256, SHA-512 hashes; verify integrity
Password Generator →
Cryptographically secure passwords with custom rules
.gitignore Generator →
Generate .gitignore for Node, Python, React, Go, Rust, Java
Robots.txt Generator →
Visual builder with AI crawler presets; block GPTBot, CCBot
JWT Builder / Generator →
Build and sign JWTs with custom claims; HS256 in-browser

References & Docs

Git Cheatsheet →
70+ Git commands + 10 rescue scenarios
Docker Cheatsheet →
80+ Docker commands — images, containers, volumes, Compose
TypeScript Cheatsheet →
Types, interfaces, generics, utility types, enums with examples
Tailwind CSS Cheatsheet →
Full v3 class reference with search
HTTP Status Code Reference →
All HTTP status codes with descriptions and use cases
React Hooks Reference →
useState, useEffect, useCallback, useMemo, useRef, custom hooks

AI & ML

Prompt Token Counter →
Estimate token count for GPT-4, Claude, Llama, Gemini + cost
Text Dataset Cleaner →
Strip HTML, URLs, whitespace; deduplicate; filter by length
Confusion Matrix Visualizer →
Auto-calculates accuracy, precision, recall, F1
Outlier Detection Tool →
IQR, Z-score, Modified Z-score with box plot visualization

Blockchain & Web3

Wallet Address Validator →
Validate Ethereum, Bitcoin, and Solana addresses
Keccak Hash Generator →
Keccak-256 / Keccak-512 as used in Ethereum (EIP-compliant)
ABI Encoder / Decoder →
Encode/decode Ethereum smart contract ABI calls
Gas Fee Calculator →
ETH gas fees in Gwei, ETH, and USD for common operations

Why DevKit?

  • Privacy-first. Everything processes in your browser. Paste your JWT, API key, or wallet address — nothing touches a server.
  • 100 tools, one tab. Stop bookmarking 100 different sites for 100 different utilities. Search across everything instantly.
  • 5 developer themes. Midnight (default), GitHub Dark, Dracula, Nord, and Monokai. It actually looks like a developer built it.
  • No friction. No newsletter modals, no signup walls, no ads. Open a tool and use it.
  • Free forever. Current phase is building organic traffic. All 100 tools are and will remain free.

FAQ

What are the best free developer tools online?

DevKit offers 100 free browser-based developer tools — JSON formatter, JWT decoder, Base64 encoder/decoder, regex tester, diff checker, SQL formatter, cURL-to-fetch converter, UUID generator, password generator, and many more. All tools run client-side with no signup required.

Are these developer tools safe to use with sensitive data?

Yes. All 100 tools in DevKit run 100% client-side — your API keys, JWTs, wallet addresses, configs, and any other sensitive data never leave your browser. There is no backend, no server processing, and no data storage.

Do I need to sign up to use DevKit?

No signup, no account, no email required. Every tool on DevKit is free and accessible instantly. Nothing is paywalled.

Does DevKit work offline?

Most tools work offline once the page has loaded, since all processing is client-side. Tools that make external requests (like the HTTP header inspector) require an internet connection.