About NiuNiu Tools

A free, privacy-first collection of online tools for developers, designers, writers, and anyone who works with data. Every tool runs entirely in your browser — no accounts, no uploads, no tracking.

What We Built and Why

NiuNiu Tools started from a simple frustration: most online utility tools are cluttered with ads, require sign-ups, send your data to unknown servers, or disappear behind paywalls after you've bookmarked them. We wanted tools that just work — fast, private, and always free.

The result is a growing collection of 15 tools covering the most common developer and productivity tasks: formatting and validating JSON and YAML, encoding and decoding data, converting between units and color formats, compressing images, generating secure passwords, and more.

Our Tools

Every tool is purpose-built to be fast and useful. Here's what's available today:

Developer Tools

  • JSON Formatter & Validator — Format, beautify, and validate JSON. Highlights syntax errors with exact line numbers.
  • YAML Formatter & Validator — Format and validate YAML documents. Catches indentation errors, duplicate keys, and invalid syntax.
  • YAML ↔ JSON Converter — Convert between YAML and JSON instantly. Auto-detects input format.
  • JSON Diff — Compare two JSON objects side by side. Normalizes key order so only real differences are highlighted.
  • YAML Diff — Compare two YAML files with semantic normalization. Essential for reviewing Kubernetes and CI/CD config changes.
  • Base64 Encoder/Decoder — Encode text or binary data to Base64, or decode Base64 strings. Full UTF-8 support.
  • URL Encoder/Decoder — Percent-encode special characters for URLs or decode encoded strings. Handles Unicode via UTF-8.
  • Password Generator — Generate cryptographically secure passwords using the Web Crypto API. Fully customizable length and character set.
  • IP Address Lookup — Look up the geographic location, ISP, and timezone of any IP address.

Converters

  • Unix Timestamp Converter — Convert between Unix timestamps and human-readable dates. Supports seconds and milliseconds.
  • Timezone Converter — Convert any datetime string between timezones. Supports ISO 8601, UTC offset notation, and non-integer offsets.
  • Color Converter — Convert colors between HEX, RGB, and HSL formats with a live visual preview.
  • Unit Converter — Convert length, weight, temperature, time, and data size between metric and imperial units.

Text & Image Tools

  • Word & Character Counter — Count words, characters, sentences, and paragraphs in real time. Includes reading time estimation.
  • Image Compressor — Compress JPEG, PNG, and WebP images locally in your browser with adjustable quality settings.

Privacy by Design

Every tool on this site processes data locally in your browser using JavaScript. No data is ever sent to our servers. This is not a policy choice — it is an architectural one. There are no servers receiving your input. You can safely use these tools with:

  • API keys and authentication tokens
  • Proprietary source code and configuration files
  • Personal documents and sensitive data
  • Internal infrastructure configs (Kubernetes manifests, CI/CD pipelines)

The only exception is the IP Lookup tool, which sends the queried IP address to a third-party geolocation API (ip.guide) to return location data. No other tool makes any network request beyond loading the page itself.

Available in 11 Languages

All tools are available in 11 languages, with localized UI, tool descriptions, usage guides, and FAQ content:

Technology

NiuNiu Tools is built with Astro, a modern static site generator that produces pure HTML with minimal JavaScript. Pages load fast because there is no JavaScript framework overhead — only the interactive tool components ship client-side code.

The site is hosted on Cloudflare Pages and served from Cloudflare's global edge network, ensuring low latency for users worldwide.

Key technical properties of every tool:

  • No server-side processing — all logic runs in the browser
  • No cookies or local storage used for tracking
  • No user accounts or sign-ups required
  • Works offline after the page is loaded (except IP Lookup)
  • Responsive design — works on desktop, tablet, and mobile
  • Dark mode support — follows your system preference

Contact & Feedback

Found a bug? Have a suggestion for a new tool? We'd love to hear from you. Visit our Contact page or email us at contact@niuniu188.net.

We regularly add new tools based on user requests. If there's a utility you find yourself reaching for repeatedly and can't find a good browser-based version of, let us know.