Free Online Developer Tools
JSON, API, Encoding & More
145+ free browser-based tools for everyday development — JSON formatter, Base64 encoder, JWT decoder, regex tester, UUID generator, SQL formatter, and much more. All running 100% client-side. Your data never leaves your device.
145+
Developer Tools
8
Categories
100%
Client-Side
Free
No Sign-Up Needed
What's New in Devkitr
15 new tools just launched — AI/LLM helpers, CSS generators & more
AI Token Counter
Count GPT-4, Claude, and Gemini tokens with estimated API cost breakdown per model.
JSON to OpenAI Function Schema
Convert JSON objects or TypeScript interfaces to OpenAI function-calling / tool-use schemas.
System Prompt Builder
Build structured AI system prompts with sections for persona, tone, constraints, and output format.
AI Prompt Diff
Compare two AI prompts side by side and highlight exactly what changed between versions.
Fake Data Generator
Generate fake names, emails, addresses, phone numbers, and more in JSON, CSV, or SQL format.
CSS Animation Generator
Build CSS @keyframes animations visually with a live preview and copy-ready CSS output.
Tailwind Color Palette Generator
Generate a full Tailwind CSS 50–950 color scale from a single hex color with ready-to-use config.
CSS Clip-Path Generator
Visually build CSS clip-path polygon, circle, and ellipse shapes with live preview.
Semantic Version Bumper
Bump major, minor, or patch versions with semver validation and changelog template generation.
Git Commit Message Generator
Generate Conventional Commits compliant git commit messages from a structured form.
SQL Query Explainer
Paste a SQL query and get a plain English breakdown of every clause explained step by step.
Password Strength Checker
Check password strength with entropy calculation, crack time estimate, and improvement suggestions.
PKCE Generator
Generate OAuth 2.0 PKCE code verifier and SHA-256 code challenge for secure authorization flows.
OpenAPI Validator
Validate OpenAPI 3.x and Swagger 2.0 YAML/JSON specs and report all structural errors.
Security Headers Checker
Paste HTTP response headers and check for missing or misconfigured security headers.
Popular Free Developer Tools
The most-used tools — JSON formatter, JWT decoder, Base64 encoder, regex tester & more
JSON Formatter
Format and beautify messy JSON data instantly with proper indentation.
Open toolJSON to CSV
Convert JSON arrays and objects to CSV format for spreadsheets and databases.
Open toolBase64 Encoder/Decoder
Encode text to Base64 or decode Base64 strings back to readable text.
Open toolJWT Decoder
Decode and inspect JSON Web Tokens to view header, payload, and signature.
Open toolSQL Formatter
SQL beautifier — format and beautify SQL queries with proper indentation online.
Open toolTimestamp Converter
Convert Unix timestamps to human-readable dates and vice versa.
Open toolUUID Generator
Generate secure, unique UUID v4 identifiers for databases and applications.
Open toolPassword Generator
Generate strong, secure, and customizable passwords for your accounts.
Open toolRegex Tester
Free online regex tester — test and debug regular expressions with real-time matching, highlighting, and capture group display. Alternative to RegExr.
Open toolWord & Character Counter
Count words, characters, sentences, paragraphs, and estimate reading time.
Open toolCase Converter
Convert text between uppercase, lowercase, title case, camelCase, snake_case, and more.
Open toolJavaScript Formatter
Beautify and format JavaScript and TypeScript code with proper indentation.
Open toolYAML to JSON
Convert YAML documents to JSON format with proper type handling.
Open toolJSON to TypeScript
Generate TypeScript interfaces and types from JSON data automatically.
Open toolQR Code Generator
Generate QR codes from text, URLs, emails, phone numbers, and Wi-Fi credentials.
Open toolJSON Schema Generator
Generate JSON Schema definitions from sample JSON data automatically.
Open toolCSS Unit Converter
Convert between px, rem, em, vh, vw, and other CSS units with configurable base size.
Open toolImage to Base64 Converter
Convert images to Base64 data URIs for embedding directly in HTML, CSS, or code.
Open toolChmod Calculator
Calculate Unix file permissions — convert between rwx notation and numeric (octal) mode.
Open toolAPI Request Tester
Free online API tester — send HTTP requests and test REST APIs in your browser.
Open toolGitignore Generator
Generate .gitignore files for any tech stack — Node.js, Python, Java, Go, and more.
Open toolCSS Flexbox Generator
Free flexbox generator — build CSS flex layouts visually with live preview.
Open toolJavaScript Minifier
Minify JavaScript code by removing whitespace, comments, and shortening variable names.
Open toolJavaScript Validator
JavaScript checker — check JavaScript code for syntax errors with detailed reporting.
Open toolCSS to SCSS Converter
Convert flat CSS into nested SCSS with proper selector grouping and variables.
Open toolHTML to JSX Converter
Convert HTML markup to valid React JSX — class→className, style strings→objects, and more.
Open toolTailwind CSS Generator
Generate Tailwind CSS classes from visual CSS property controls.
Open toolJSON to C# Class Generator
Generate C# POCO classes from JSON objects automatically.
Open tool.htaccess Generator
Generate Apache .htaccess rules for redirects, security, and caching.
Open toolCurl to Code Converter
Convert cURL commands to JavaScript, Python, PHP, Go, and more.
Open toolJSON Tree Viewer
Visualize JSON data as an interactive collapsible tree structure.
Open toolCrontab Generator
Build cron schedule expressions visually with a human-readable preview.
Open toolXML to JSON Converter
Convert XML data to JSON format with attribute handling options.
Open toolMarkdown Table Generator
Build Markdown tables visually with a spreadsheet-like editor.
Open toolGit Command Generator
Build complex Git commands visually with options and flag explanations.
Open toolBcrypt Hash Generator
Generate and verify bcrypt password hashes with configurable salt rounds.
Open toolIP Subnet Calculator
Calculate IP subnets, CIDR ranges, network addresses, and host counts.
Open toolJSON to Go Struct
Generate Go struct definitions from JSON data with proper tags.
Open toolJSON to Python Dataclass
Generate Python dataclass definitions from JSON data.
Open toolJSON to SQL INSERT
Generate SQL INSERT statements from JSON arrays or objects.
Open toolREADME.md Generator
Generate professional GitHub README files with badges, sections, and TOC.
Open toolCode Screenshot Generator
Create beautiful code screenshots with syntax highlighting and custom themes.
Open toolTailwind CSS to Vanilla CSS
Convert Tailwind CSS utility classes to equivalent vanilla CSS.
Open toolWebSocket Tester
Connect to WebSocket endpoints, send/receive messages, and inspect real-time traffic.
Open toolGraphQL Playground
Write and execute GraphQL queries with variables, headers, and response viewer.
Open toolOpenAPI / Swagger Viewer
Free online Swagger editor and OpenAPI viewer — paste Swagger YAML/JSON and render interactive Swagger UI API documentation instantly.
Open toolRSA Key Pair Generator
Generate RSA public/private key pairs in PEM format for encryption and signing.
Open toolTOTP / 2FA Generator
Free online 2FA code generator and authenticator tool — generate TOTP secrets, 2FA codes, and test two-factor authentication instantly.
Open toolAST Explorer
Paste JavaScript or TypeScript code and view the AST (Abstract Syntax Tree) visually.
Open toolRegex Debugger
Step-by-step regex matching visualization with capture group highlighting.
Open toolTypeScript Playground
Write TypeScript and see compiled JavaScript output in real-time.
Open toolJSON Schema Validator
Validate JSON data against a JSON Schema with detailed error reporting.
Open toolCron Job Visualizer
Free cron expression generator, translator, and visual timeline — see exactly when your cron job fires over days and weeks. Alternative to crontab guru.
Open toolSQL to Prisma Schema
Convert SQL CREATE TABLE statements to Prisma schema models instantly.
Open toolOpenAPI to TypeScript
Generate TypeScript interfaces and types from OpenAPI specifications.
Open toolNginx Config Generator
Visual builder for Nginx server blocks — reverse proxy, SSL, gzip, and more.
Open toolGitHub Actions Generator
Build CI/CD workflow YAML files with a visual builder for GitHub Actions.
Open toolDockerfile Generator
Generate optimized Dockerfiles based on runtime, framework, and options.
Open toolAI Token Counter
Count GPT-4, Claude, and Gemini tokens with estimated API cost breakdown per model.
Open toolJSON to OpenAI Function Schema
Convert JSON objects or TypeScript interfaces to OpenAI function-calling / tool-use schemas.
Open toolFake Data Generator
Generate fake names, emails, addresses, phone numbers, and more in JSON, CSV, or SQL format.
Open toolDeveloper Tools by Category
JSON tools, API utilities, encoding, formatters, converters, generators & more — organized by use case
JSON Tools
10 toolsFormat, validate, compare, and convert JSON data with powerful online utilities.
API & Web Tools
11 toolsTest APIs, inspect HTTP headers, parse user agents, and debug web requests.
Encoding & Security
14 toolsBase64, JWT, SHA256, MD5, bcrypt, and other encoding and hashing utilities.
Formatters & Beautifiers
15 toolsBeautify and format SQL, HTML, CSS, JavaScript, XML, and YAML code instantly.
Converters
38 toolsConvert between CSV, JSON, XML, YAML, timestamps, and color codes seamlessly.
Generators
33 toolsGenerate UUIDs, passwords, lorem ipsum, slugs, QR codes, and CSS gradients.
Dev Utilities
20 toolsGeneral-purpose developer utilities including regex tester, diff checker, and more.
AI & LLM Tools
4 toolsToken counting, prompt builders, function schema generators, and other AI/LLM developer utilities.
How Our Developer Tools Work
Three-step workflow — paste, process in-browser, copy results. No server, no upload, no waiting
Paste Your Code or Data
Copy your JSON, SQL, HTML, CSS, or any code/data into the tool input. Supports pasting from IDEs, terminals, API responses, or files.
Processed Instantly In-Browser
Your data is processed entirely in your browser using JavaScript and the Web Crypto API. No server calls, no upload, no latency.
Copy the Result & Move On
Copy the formatted, converted, encoded, or generated result to your clipboard in one click. Download as a file when needed.
Why Developers Choose Devkitr
Privacy-first, instant, and completely free — developer tools done right
100% Private — No Data Uploaded
Every tool runs entirely in your browser. Your JSON, code, tokens, and passwords never touch any server.
Instant Results — No Server Lag
No loading screens. No server round trips. Your JSON, code, and data are processed in milliseconds — right in your browser.
Completely Free — No Account Needed
No sign-ups, no rate limits, no paywalls. Every developer tool is free for personal, educational, and commercial use.
What Is Devkitr? — Your All-in-One Online Developer Toolkit
Devkitr is a free, browser-based toolkit built for software engineers, web developers, DevOps engineers, QA testers, and technical writers. It brings together 145+ utilities across 8 categories — JSON tools, API testers, encoding and security helpers, code formatters, data converters, config generators, and everyday dev utilities — all in one place with zero installation or sign-up required.
Every tool on Devkitr processes data entirely inside your browser using JavaScript and the Web Crypto API. Nothing is uploaded to a server, nothing is logged, and nothing is stored. This client-side architecture means your API keys, passwords, tokens, code snippets, and configuration data stay on your device at all times — making Devkitr safe to use with sensitive or production data.
Whether you need to format a JSON response from an API, decode a JWT to debug authentication, generate TypeScript interfaces from a JSON payload, or scaffold a Dockerfile for a new project, Devkitr provides the tool — instantly, with no setup overhead.
Who Is Devkitr For?
Frontend Developers
JSON formatting, CSS generators, HTML-to-JSX conversion, Tailwind utilities, color converters, and meta tag generation.
Backend Engineers
JWT decoding and signing, bcrypt hashing, API request testing, SQL formatting, timestamp conversion, and config file generation.
DevOps & SRE
Dockerfile and Docker Compose generators, Nginx config builder, GitHub Actions YAML, crontab builder, chmod calculator, and IP subnet calculator.
Mobile Developers
JSON to Dart, Kotlin, and Swift converters for creating model classes from API responses in Flutter, Android, and iOS projects.
How Is Devkitr Different?
Most online developer tools either require creating an account, send your data to remote servers for processing, or limit usage behind paywalls. Devkitr takes a different approach: every tool is open, free, and runs locally. The source code handles parsing, formatting, conversion, and generation directly in the browser using established libraries and standards-compliant algorithms. There are no API calls, no rate limits, and no data collection — your workflow stays private and uninterrupted.
Devkitr is also built as a progressive web app. After the initial page load, tools work even with an unstable internet connection. This makes it useful for developers working on flights, in cafes with poor Wi-Fi, or behind restrictive corporate firewalls that block third-party SaaS tools.
All 145 Free Online Developer Tools
Complete directory — every tool, free, browser-based, no sign-up required
JSON Tools
10API & Web Tools
11Encoding & Security
14Formatters & Beautifiers
15Converters
38Generators
33Dev Utilities
20Ready to streamline your workflow?
Format, convert, encode, generate, and validate — all from one place. No sign-up, no limits, 100% free.
Frequently Asked Questions
Everything you need to know about Devkitr
Is Devkitr really free to use?+
Yes, completely free. Every tool on Devkitr is available at no cost with no sign-up, no rate limits, and no hidden paywalls. We are funded by non-intrusive advertising and are committed to keeping the tools free for all developers.
Do my data and code stay private?+
Absolutely. Every tool on Devkitr processes data entirely inside your browser using JavaScript. Nothing is uploaded to any server, nothing is logged, and nothing is stored. You can verify this yourself by opening your browser's Network tab — you'll see zero data sent for any tool operation.
Do I need to create an account?+
No account is required for any tool. You can use all tools instantly without signing up, logging in, or providing an email address.
What kinds of developer tools does Devkitr offer?+
Devkitr offers 145+ tools across 8 categories: JSON formatting, validation, and conversion; API request testing and HTTP header inspection; encoding and security tools like Base64, JWT, SHA-256, and bcrypt; code formatters for SQL, HTML, CSS, and JavaScript; data converters between JSON, CSV, XML, and YAML; code generators for UUIDs, passwords, Docker, and GitHub Actions; and developer utilities like regex tester, diff checker, and cron parser.
Does Devkitr work offline?+
Yes. Devkitr is built as a Progressive Web App (PWA). After the first page load, tools continue to work even without an internet connection. This makes it useful when working on flights, in locations with unreliable Wi-Fi, or behind restrictive network firewalls.
How do I suggest a new tool?+
We welcome tool suggestions. Send your idea to suggest@devkitr.com or use the Contact page. Tell us what the tool does and why it would be useful. We prioritize tools based on community demand.