Free Developer Tools
& Web Utilities

Tools we built because we got tired of pasting sensitive data into random sites and wondering what happened to it. Everything runs in your browser. Nothing goes to a server. No account, no tracking, no "sign up to continue."

6
Free Tools
100%
Client-Side
0
Data Collected
Featured Tool

TimeVault — Send a Message Through Time

TimeVault lets you write a message today that no one — not even us — can read until a specific future date. Think of it as a digital time capsule: lock it, share the link, and it only opens when the moment arrives.

Every message is encrypted inside your browser using AES-256 before it ever leaves your device. The unlock date itself is part of the key, so early decryption is mathematically impossible — not just policy.

✉️ Letter to future self 🎁 Gift & surprise reveals 📅 Anniversary messages 🎓 Graduation notes 📢 Timed announcements 🏆 Milestone unlocks
🔒

End-to-end encrypted, always Your message is encrypted in the browser with AES-256 before upload. The decryption key is derived from the unlock timestamp — we store only ciphertext and can never read your content before or after the unlock date.

Shareable unlock links
Any timezone supported
No account required
Rich text formatting
Create a Time Capsule How it works →
🔒
Time Capsule
LOCKED · Opens Dec 25, 2026
To: Future Me Created: Mar 2026
Unlocks in 289 days, 14 hours
AES-256 · Client-side encrypted · curiousutilities.com
How It Works

Simple, Fast, Private

Our tools are designed to respect your privacy while providing powerful functionality. Everything happens in your browser, nothing is sent to our servers.

1

Choose Your Tool

Select from our collection of developer utilities. Each tool is purpose-built to solve a specific problem efficiently.

2

Use Instantly

No registration, no login, no waiting. Just paste your data and get instant results. Works on any device with a modern browser.

3

Your Data Stays Yours

All processing happens locally in your browser using JavaScript. Your sensitive data never touches our servers.

Our Tools

Everything You Need, Nothing You Don't

Each tool is carefully designed to solve real problems developers face every day. Built with simplicity and performance in mind.

JSON Formatter
Paste your JSON and it formats instantly — syntax highlighted, errors flagged with exact line numbers. Minify it, expand it, view it as a tree. Nothing leaves your browser.
Learn more about JSON Formatter
JWT Decoder
See exactly what's in your JWT — header, payload, claims, expiry — without sending it anywhere. The reason we built this: we got tired of not knowing where our tokens went when we used other decoders.
Learn more about JWT Decoder
Unix Timestamp Converter
Because 1741651200 is not a human-readable date. Paste a timestamp, get a date. Or pick a date, get a timestamp. Handles seconds and milliseconds, any timezone.
Learn more about Unix Timestamp
Timezone Visualizer
Stop doing timezone math in your head. See multiple timezones side by side — useful for distributed teams, scheduling releases, or figuring out if your colleague in Singapore is awake yet.
Learn more about Timezone Visualizer
Featured
TimeVault
Write a message that nobody — including us — can read until a specific date. Encrypted in your browser with AES-256 before it goes anywhere. The unlock date is part of the key, so early decryption isn't just against the rules; it's mathematically impossible.
Learn more about TimeVault
Cloud Cost Calculator
Get a real cost estimate before your first AWS bill surprises you. Compare compute, storage, and networking across AWS, Azure, and GCP in one place, instead of juggling three different pricing pages.
Learn more about Cloud Cost Calculator
Why Choose Us

Built Different, On Purpose

We believe developer tools should be fast, private, and free from unnecessary complexity.

Privacy First

Your data never leaves your browser. We use client-side JavaScript for all processing, which means your sensitive information—API keys, tokens, configuration files—stays on your device. No server logs, no analytics on your data, no tracking.

Lightning Fast

No bloated frameworks, no unnecessary dependencies. Our tools are built with vanilla HTML, CSS, and JavaScript for maximum performance. They load instantly and work offline after the first visit. Your workflow stays uninterrupted.

Developer Experience

Clean, intuitive interfaces designed by developers for developers. No cluttered UIs, no confusing options. Each tool does one thing well with sensible defaults and advanced options when you need them.

Always Free

No premium tiers, no feature gates, no "sign up for more." Every tool is completely free with full functionality. We believe essential developer utilities shouldn't cost money or require accounts.

Built for Developers,
by Developers

Curious Utilities started as an internal toolkit—a collection of utilities our team built to solve everyday problems in our development workflow. We got tired of using tools that were slow, required logins, or sent our data to unknown servers.

Every tool is designed with the same principles: fast loading times, clean interfaces, and complete privacy. Your data never leaves your browser, and we never ask for your email or personal information.

Read our full story
  • No account required — just open and use
  • 100% client-side — your data stays local
  • Mobile friendly — works on any device
  • Always free — no premium tiers or paywalls
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2 "name": "curious-utilities",
3 "version": "1.0.0",
4 "tools": 6,
5 "dataCollected": null,
6 "openSource": true,
7 "free": true
8 }
Resources

Developer Guides & Tutorials

Learn about the technologies behind our tools with in-depth guides and practical tutorials.

Guide

Understanding JSON: A Complete Guide for Developers

Learn what JSON is, its syntax, common use cases, and best practices for working with JSON data in your applications.

Read article
Security

JWT Tokens Explained: How They Work and When to Use Them

Understand the structure of JSON Web Tokens, how authentication flows work, and security best practices.

Read article
Tutorial

Unix Timestamps: What They Are and How to Work With Them

Master Unix time, learn conversion techniques, and avoid common pitfalls when handling timestamps.

Read article
View all articles
FAQ

Frequently Asked Questions

Common questions about Curious Utilities and how our tools work.

Are all tools really free?
Yes, all tools on Curious Utilities are completely free with no hidden costs, no premium tiers, and no feature limitations. We believe essential developer tools should be accessible to everyone.
Is my data safe?
Your data never leaves your browser. All processing happens locally using JavaScript. We don't collect, store, or transmit any data you enter into our tools. Your sensitive information stays on your device.
Do I need to create an account?
No account required. Just open any tool and start using it immediately. We don't ask for your email, name, or any personal information. No signup forms, no login screens.
What browsers are supported?
Our tools work on all modern browsers including Chrome, Firefox, Safari, and Edge. They're also fully responsive and work on mobile devices and tablets.
Can I use these tools offline?
Most of our tools work offline after the initial page load since all processing is done client-side. Simply load the tool once, and it will continue to work even without an internet connection.
How can I suggest a new tool?
We love hearing from developers! Send your suggestions to contact@curiousutilities.com. We review every request and prioritize tools that solve real problems for the developer community.
View all FAQs

Have Ideas or Feedback?

Want to suggest a new tool, report a bug, or just say hello? We'd love to hear from you.

contact@curiousutilities.com