A curated list of free developer tools that work instantly -- no account creation, no signup, no login. Just open and use.
Why this list? Developers constantly reach for quick online tools -- format some JSON, test a regex, decode a JWT. But too many tools demand you create an account before you can do anything. Every tool on this list lets you get straight to work with zero friction. If it requires signup to use basic functionality, it does not belong here.
- JSON Tools
- Regex Tools
- API Testing & HTTP
- Code Formatters & Linters
- Encoding & Conversion
- Generators
- Diff & Comparison
- Diagramming & Visualization
- Performance & Testing
- CSS Tools
- DNS & Network
- Miscellaneous
- Contributing
- Disclaimer
- JSONLint - A JSON validator that checks your JSON syntax and highlights errors with helpful messages.
- JSON Formatter & Validator - Format, validate, and minify JSON data with configurable indentation and RFC compliance checks.
- jq play - An online playground for jq, the command-line JSON processor. Write and test jq filters in the browser.
- JSON Crack - Visualize JSON data as interactive graphs and tree diagrams to understand complex structures at a glance.
- JSON Path Finder - Paste JSON and click on any value to get its path, making it easy to write selectors for deeply nested data.
- regex101 - Build, test, and debug regular expressions with real-time explanations, match highlighting, and a quick reference.
- Regexr - Learn, build, and test regular expressions with an interactive interface, cheatsheet, and community patterns.
- Debuggex - Visualize regular expressions as railroad diagrams so you can see exactly how your pattern matches.
- Hoppscotch - An open-source API development ecosystem for designing, testing, and documenting APIs directly in the browser.
- ReqBin - Send HTTP requests online and inspect responses. Supports REST, SOAP, and raw HTTP methods.
- httpbin.org - A simple HTTP request and response service for testing clients, debugging, and experimenting with HTTP.
- Webhook.site - Instantly inspect, test, and debug incoming webhooks and HTTP requests with a unique temporary URL.
- curl converter - Convert curl commands to Python, JavaScript, Go, PHP, and dozens of other languages instantly.
- Prettier Playground - The official online playground for Prettier. Format JavaScript, TypeScript, HTML, CSS, JSON, and more.
- Black Playground - Try the Black Python code formatter in the browser. Paste code and see the formatted result instantly.
- ShellCheck - Paste a shell script and get warnings, suggestions, and fixes for common bash/sh pitfalls.
- SQL Formatter - Format messy SQL queries into clean, readable, indented SQL with configurable dialect support.
- HTMLHint - A static code analysis tool for HTML that identifies common mistakes and enforces best practices.
- Base64 Encode/Decode - Encode or decode Base64 strings and files directly in the browser.
- URL Encoder/Decoder - Encode or decode URLs and query strings with percent-encoding.
- JWT.io - Decode, verify, and inspect JSON Web Tokens. Paste a JWT to see its header, payload, and signature.
- CyberChef - The "cyber swiss army knife" for encoding, decoding, hashing, encryption, compression, and data analysis -- hundreds of operations in one tool.
- Unix Timestamp Converter - Convert Unix timestamps to human-readable dates and vice versa, with support for multiple formats.
- UUID Generator - Generate UUIDs (v1, v4, and more) individually or in bulk, ready to copy.
- Lorem Ipsum Generator - Generate placeholder text in paragraphs, sentences, or words for mockups and design.
- Mockaroo - Generate realistic test data in CSV, JSON, SQL, and other formats with customizable schemas. Basic use requires no signup.
- crontab.guru - A cron schedule expression editor that translates cron syntax into plain English and vice versa.
- readme.so - Build a project README quickly using pre-built sections that you drag, drop, and edit.
- gitignore.io - Generate
.gitignorefiles for any combination of operating systems, IDEs, and programming languages. - Carbon - Create and share beautiful images of your source code with customizable themes, fonts, and window styles.
- Ray.so - Generate elegant code screenshots with syntax highlighting, dark mode, and gradient backgrounds.
- Diffchecker - Compare text, images, PDFs, and folders online to find differences instantly.
- Text Compare - A simple side-by-side text comparison tool that highlights every difference between two inputs.
- Meld - A visual diff and merge tool for files and directories. Free and open-source desktop application.
- Excalidraw - A virtual whiteboard for sketching diagrams with a hand-drawn look. Real-time collaboration included.
- draw.io / diagrams.net - A full-featured diagramming tool for flowcharts, UML, network diagrams, and more. Runs entirely in the browser.
- Mermaid Live Editor - Write diagrams as markdown-like text and render flowcharts, sequence diagrams, Gantt charts, and more in real time.
- D2 Playground - Try D2, a modern declarative diagramming language, directly in the browser with live rendering.
- dbdiagram.io - Design database diagrams by writing DSL markup. Visualize tables, relationships, and export SQL. Basic use requires no signup.
- PageSpeed Insights - Google's tool for analyzing web page performance on mobile and desktop with actionable recommendations.
- GTmetrix - Test your website's loading speed and get a detailed performance report with Lighthouse and CWV metrics. Basic tests require no signup.
- WebPageTest - Run free website speed tests from multiple locations around the world with detailed waterfall charts.
- Lighthouse - An open-source auditing tool built into Chrome DevTools for performance, accessibility, SEO, and best practices.
- CSS Grid Generator - Visually build CSS Grid layouts by setting rows, columns, and gaps, then copy the generated code.
- Flexbox Froggy - Learn CSS flexbox interactively by writing CSS to guide a frog to its lily pad.
- CSS Gradient Generator - Create linear and radial CSS gradients visually with a color picker and copy the resulting CSS.
- Animista - Browse, customize, and generate CSS animations on demand with live previews and ready-to-use code.
- Clippy - A CSS
clip-pathmaker that lets you create complex shapes visually and export the CSS.
- dig (online) - Google's online DNS lookup tool. Query any DNS record type for any domain.
- nslookup.io - Look up DNS records for any domain with a clean interface and support for all record types.
- MXToolbox - Comprehensive DNS, email, and network diagnostic tools including MX lookup, blacklist checks, and SMTP testing.
- WhatIsMyIP.com - See your public IP address instantly along with geolocation, ISP details, and proxy detection.
- SSL Labs - Deep analysis of any web server's SSL/TLS configuration with grading and detailed findings.
- explainshell.com - Paste a shell command and get a breakdown of every argument, flag, and option with man page excerpts.
- tldr pages - Simplified, community-driven man pages with practical examples for common command-line tools.
- DevDocs - A unified API documentation browser with instant search across hundreds of languages, frameworks, and tools.
- Can I Use - Up-to-date browser compatibility tables for HTML, CSS, JavaScript, and web platform features.
- Bundlephobia - Find the cost of adding an npm package to your bundle -- see size, download time, and composition.
- npm trends - Compare npm package download counts over time to evaluate popularity and make informed choices.
| Repository | Description |
|---|---|
| Chrome Privacy Extensions | Curated Chrome extensions for privacy and security |
| Custom GPTs | Community-curated catalog of useful Custom GPTs with ratings |
| AI Agents | Practical AI agents, frameworks, and tools for developers |
| FinOps Tools | Vendor-neutral tools for cloud cost optimization |
| Local-First Tools | Local-first, offline-capable, privacy-respecting tools |
| AI & LLM Papers | Foundational and frontier AI/LLM research papers reading list |
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Want to add a tool or suggest an improvement? Pull requests are welcome. See our CONTRIBUTING.md for guidelines.
The one rule: every tool you submit must work without creating an account. If basic functionality requires signup or login, it does not belong on this list.
The tools listed here are compiled from community contributions and personal research. We are not affiliated with any of the tools or their developers. Please review and verify before relying on any tool for sensitive data.