Free Online Toolbox

Handy utilities for developers and everyday office work, all running locally in your browser. Your files never leave your computer. No sign-up, no limits.

Processed locally, data never sent out Ready to use, no sign-up needed Completely free, unlimited use

All tools (18)

JSON Formatter

Paste JSON to beautify, minify or escape it, with syntax errors pinpointed and optional key sorting.

Developer favourite

Base64 Encode / Decode

Two-way conversion between text and Base64, with URL-safe mode. Fully local, no data is sent.

Privacy first

Timestamp Converter

Convert between Unix timestamps and dates, automatically detecting seconds or milliseconds, with multi-timezone comparison.

Backend debugging

Regex Tester

Highlight matches live, list every match and capture group, with all common flags supported.

Live preview

Cron Expression Explainer

Turn an unreadable schedule expression into plain language, predict the next 10 run times, with 5-field and 6-field support.

Ops troubleshooting

Word Counter

Count characters, words, lines and paragraphs, estimate reading time, with hints for WeChat articles and academic papers.

Writing essential

Text Diff

Paste two passages and see additions, deletions and changes line by line, down to character-level differences. Ideal for proofreading.

Proofreading

Markdown Preview

Write on the left, render instantly on the right. Tables, code blocks and task lists supported; copy the HTML or download the .md file.

Write and see

Text Dedupe & Sort

Bulk dedupe by line, natural sort, random shuffle, case conversion and trailing-space cleanup. Great for tidying up name lists.

Data cleanup

Chinese Character Lookup

Look up stroke count, radical, pinyin and meaning; reverse-search all characters by stroke count or radical. All 6763 GB2312 characters included.

Language study

QR Code Generator

Four modes: URL, text, WiFi password and digital business card. Choose error-correction level and colours; download PNG or SVG.

Generated locally

QR Code Decoder

Upload a QR code image to read its content, showing error-correction level and version. Check where it points before you scan.

Check before scanning

Image Compressor

Batch-compress JPG, PNG and WebP, adjustable quality and max edge length, with before/after size comparison. Images are never uploaded.

Local processing

Colour Converter

Convert instantly between HEX, RGB, HSL, HSV and CMYK, with matching palettes and a WCAG contrast check.

Design & colours

Unit Converter

One-click conversion for length, area, weight, volume, temperature, speed, data storage and more.

Everyday use

Date Calculator

Work out how many days, weeks or months lie between two dates, count working days excluding weekends, or project a date by adding days.

Deadline maths

Mortgage Calculator

Compare equal instalments with equal principal, month-by-month repayment schedule, supporting commercial, housing-fund and combined loans.

Essential for buyers

Income Tax Calculator

Calculate take-home pay with the latest special additional deductions, including social insurance, housing fund and year-end bonus options.

Take-home pay

Practical guides

The principles behind each tool and the pitfalls we hit. These are things we actually looked up, calculated and verified while building the tools — not generic claims copied from the web.

Why do stroke counts differ from the dictionary? Equal instalments or equal principal: which to choose? Why do Chinese QR codes take up more space than English ones?

About this site

This is an online toolbox focused on single-purpose small tools. Unlike the tool sites you usually find, every tool here does its calculations locally in your browser — the content you paste and the files you upload never pass through any server.

You can verify this yourself: open the developer tools with F12, switch to the Network panel and perform an action. You will see that no request carrying your data is ever sent.

Why we insist on local processing

  • Beautify, minify, escape, sort by key, with syntax error location
  • Two-way text conversion, URL-safe charset, correct handling of Chinese
  • Unix timestamps and dates, automatic unit detection, multi-timezone

All tools at a glance

Development

  • JSON Formatter —— Beautify, minify, escape, sort by key, with syntax error location
  • Base64 Encode / Decode —— Two-way text conversion, URL-safe charset, correct handling of Chinese
  • Timestamp Converter —— Unix timestamps and dates, automatic unit detection, multi-timezone
  • Regex Tester —— Live highlighting, capture groups, common regex cheatsheet
  • Cron Expression Explainer —— Field-by-field explanation, next 10 run times, common expression cheatsheet
  • Markdown Preview —— Write and see it rendered live, tables, code blocks and task lists

Writing

  • Word Counter —— Multi-dimensional counts, hints for WeChat articles and academic papers
  • Text Diff —— Line-by-line plus character-level highlighting, proofread without installing anything
  • Text Dedupe & Sort —— Bulk dedupe, natural sort, shuffle, case conversion, trailing-space cleanup
  • Chinese Character Lookup —— Stroke count, radical, pinyin and meaning, with reverse search by stroke or radical

Images & design

  • QR Code Generator —— URL, text, WiFi and business card modes, SVG and PNG download
  • QR Code Decoder —— Read a QR code from an image, showing level and version — see clearly what it points to before scanning
  • Image Compressor —— Batch-compress JPG / PNG / WebP, adjust quality and max edge, compare sizes
  • Colour Converter —— Convert between five colour formats, with palette suggestions and accessibility contrast checks

Everyday & finance

  • Unit Converter —— Length, weight, area, volume, temperature, speed, storage
  • Date Calculator —— Days apart, working-day count, projecting a date, with leap years and inclusive counting explained
  • Mortgage Calculator —— Equal instalments / equal principal comparison and a monthly repayment table
  • Income Tax Calculator —— Special additional deductions, social insurance and housing fund, year-end bonus options compared

A technical note on "local processing"

These tools have no backend. Once the page has loaded they stop talking to any server. QR encoding, colour-space conversion, text diffing, mortgage and tax formulas are all computed directly by JavaScript in the page. The character data is loaded as text alongside the page, so lookups generate no network requests either.

Because no server compute is consumed, the site can stay free and unlimited for the long term. If a tool you need is missing, let us know and we will keep adding.