Small web tools

A growing collection of small, self-contained web tools — one idea at a time.

• Markdown Previewer

  Type Markdown and see it rendered as HTML instantly. You can also copy the generated HTML.

  • テキスト

• Running Pace Calculator

  Given any two of distance, time, and pace, calculate the third. Useful for estimating race times or target paces.

  • 計算
  • 生活

• Loan Repayment Calculator

  Calculate the monthly payment, total repayment, and total interest from a loan amount, annual rate, and term.

  • 計算
  • 生活

• Password Generator

  Generate a secure random password in your browser by choosing character types and length. Shows the estimated strength (entropy) too.

  • 生活

• Color Converter

  Convert colors between HEX, RGB, and HSL.

  • 開発
  • 変換

• JWT Decoder

  Decode and format a JWT (JSON Web Token) header and payload. Does not verify the signature.

  • 開発

• Morse Code Translator

  Convert between text and Morse code, and listen to it as sound.

  • テキスト
  • 生活

• Percentage Calculator

  Calculate percentages three ways: share of a whole, a percent of a number, and percent change.

  • 計算
  • 生活

• Unit Converter

  Convert between units of length, weight, volume, and temperature.

  • 計算
  • 変換

• Text Case Converter

  Convert text into camelCase, snake_case, kebab-case, and other common cases all at once.

  • 開発
  • テキスト

• UUID Generator

  Generate random UUIDs (v4). Supports batch generation, uppercase, and hyphen-free formatting.

  • 開発

• Roman Numeral Converter

  Convert between Arabic numbers (1–3999) and Roman numerals.

  • 変換

• Number Base Converter

  Convert between binary, octal, decimal, hexadecimal, and any custom base from 2 to 36.

  • 開発
  • 変換

• Pomodoro Timer

  A pomodoro timer that alternates work and breaks, with adjustable durations and session count.

  • 生活

• BMI & Ideal Weight Calculator

  Calculate BMI from height and weight, with a weight category and the difference from the reference weight at BMI 22.

  • 計算
  • 生活

• Random Picker (Lottery Draw)

  Enter a list of candidates, one per line, and randomly pick one or more. Optionally allow repeats.

  • 生活

• Base64 / URL Encoder

  Convert text to and from Base64 and URL encoding.

  • 開発

• Regex Tester

  Test a regular expression against sample text, with live match highlighting and capture groups.

  • 開発

• Text Diff

  Compare two texts and highlight the lines that were added or removed.

  • テキスト

• Bill Splitter

  Split a total bill evenly among a group, with optional service charge and round-up to avoid coming up short.

  • 計算
  • 生活

• Date Calculator

  Calculate the number of days between two dates, or add/subtract days, weeks, months, or years from a date.

  • 計算
  • 日付

• Timestamp Converter

  Convert between Unix timestamps and dates, with timezone selection.

  • 開発

• Character Counter

  Count characters, words, lines, and bytes. Includes a manuscript-paper estimate and social media limit checks.

  • テキスト

• JSON Formatter

  Format, minify, and validate JSON, with error positions for broken input.

  • 開発
  • テキスト

• Hash Calculator

  Calculate MD5, SHA-1, SHA-256, SHA-384, and SHA-512 for text or files.

  • 開発