Editor's Picks
JSON Formatter
Pretty-print, minify, or validate JSON with error location hints.
Bilingual Tone Checker
Paste a message, see how warm, formal, or direct it reads.
Compound Interest / CAGR Calculator
Model compound growth from a starting amount, monthly contributions, annual return, and years — or backsolve CAGR from start and end values. Year-by-year curve.
Gomoku
Play gomoku against AI with live threat visualization that teaches you board patterns as you play.
Color Converter
Convert between HEX, RGB, and HSL live — with WCAG contrast ratios and nearest CSS color name.
Taiwan ID Validator
Check Taiwan national ID format, checksum, and prefix.
This Week
Bilingual Tone Checker
Paste a message, see how warm, formal, or direct it reads.
JSON Formatter
Pretty-print, minify, or validate JSON with error location hints.
Forgetting Curve Vocab
Learn English vocabulary using Ebbinghaus forgetting curve spaced repetition. 5 minutes a day with pronunciation and example sentences.
Explore by Category
AI
- Bilingual Tone Checker
- Token Visualizer
Quant
- Compound Interest / CAGR Calculator
- DCA Calculator
- Kelly Calculator
Dev
- Base64 Encoder / Decoder
- CSS Minifier / Beautifier
- File to Markdown
Games
- Block Stack
- Five-Letter Grid
- Gomoku
Local
- ROC / Gregorian Year Converter
- Taiwan ID Validator
- Uniform Invoice Validator
Design
- Aspect Ratio Calculator
- Color Converter
- Image Compressor
Text
- Character Word Counter
- Diff Checker
- Markdown Cleaner
Time
- Breath Pacer
- Unix Timestamp Batch Converter
Learn
- Bopomofo Practice
- Chengyu Guess
- Chord Finder