All apps
A list of all tools on apps.henryyang.tw.
StaySplit
Split lodging costs fairly when people stay different nights (optional fixed fee).
Business-day calculator
Convert โN business daysโ into a real date. Add holidays. Clear rules.
Guitar Practice
Metronome, practice timer, chord cheatsheet, and simple local practice log.
Timestamp converter
Convert Unix timestamps โ datetime. Supports seconds/milliseconds and UTC/local display.
Epoch converter
Convert Unix epoch โ datetime with auto-detect (seconds/milliseconds). Shows UTC/local and a relative โfrom nowโ hint.
JSON prettifier
Prettify or minify JSON locally. Shows parse errors with line/column hints. Copy output or share a link. Browser-only MVP.
JSON prettify
Prettify or minify JSON locally. Optional key sorting. Copy output or share a link. Browser-only MVP.
CSV to JSON converter
Convert CSV to JSON locally (header option, delimiter, quoting). Copy JSON or share a link. Browser-only MVP.
TSV to JSON converter
Convert TSV (tab-separated values) to JSON locally (header option, quoting). Copy JSON or share a link. Browser-only MVP.
JSON to CSV converter
Convert JSON to CSV locally (flatten nested keys, delimiter, quoting). Copy CSV or share a link. Browser-only MVP.
JSON diff
Compare two JSON documents locally. Shows added/removed/changed paths. Output as human-readable text or JSON Patch (RFC 6902). Copy results or share a link.
JSON Schema validator
Validate JSON against a JSON Schema locally. Shows clear error paths. Copy results or share a link. Browser-only MVP.
Cron parser
Parse a 5-field cron expression locally and preview the next run times (local or UTC). Copy results or share a link.
JSON to YAML converter
Convert JSON to YAML locally in your browser. Optional key sorting and quoting. Copy output or share a link. Browser-only MVP.
YAML to JSON converter
Convert YAML to JSON locally in your browser. Optional pretty print and key sorting. Copy output or share a link. Browser-only MVP.
Base64 encoder/decoder
Encode or decode Base64 locally (supports URL-safe and optional no padding). Shows byte size. Copy output or share a link. Browser-only MVP.
Base64 encode/decode (text + file)
Encode/decode Base64 locally, plus file โ Base64 data URL conversion. Copy output or download a file. Shareable link for text mode. Browser-only MVP.
URL encode/decode
Encode/decode URL text locally (encodeURIComponent/encodeURI). Includes โ+ as spaceโ decoding for query strings. Copy output or share a link. Browser-only MVP.
MD5 calculator
Compute MD5 for a text input locally in your browser (hex + Base64). Copy results or share a link. Includes a security warning. Browser-only MVP.
SHA-1 calculator
Compute SHA-1 for a text input locally in your browser (hex + Base64). Copy results or share a link. Includes a security warning. Browser-only MVP.
SHA-256 calculator
Compute SHA-256 for a text input locally in your browser (hex + Base64). Copy results or share a link. Browser-only MVP.
SHA-512 calculator
Compute SHA-512 for a text input locally in your browser (hex + Base64). Copy results or share a link. Browser-only MVP.
SHA3-256 calculator
Compute SHA3-256 for a text input locally in your browser (hex + Base64). Copy results or share a link. Browser-only MVP.
JWT decoder
Decode a JWT locally to view header and payload JSON. Shows common claims and converts iat/nbf/exp to dates. Copy JSON or share a link. No signature verification. Browser-only MVP.
JWT encoder
Create a JWT locally by editing header/payload JSON and choosing HS256 or none. Shows base64url parts and lets you copy the token or share a link. Browser-only MVP.
HTTP status codes lookup
Search HTTP response status codes (1xxโ5xx) by code or keyword. Filter, copy, and share a link. Browser-only MVP.
curl to Fetch
Convert a curl command into a JavaScript fetch() example. Browser-only string conversion (no requests). Copy output or share a link. MVP.
Notice period end date calculator
Calculate when a notice period ends (calendar days, business days, weeks/months) with weekends + holidays and explicit counting rules.
Timezone overlap planner
Pick a date and 2โ6 timezones, set each personโs availability window, and find the best overlap time. DST-aware and shareable.
Prorated rent calculator
Calculate prorated rent for moving in/out mid-month (multiple methods).
Unit price calculator
Compare deals by unit price (per g/ml/piece) so you can pick the best value fast.
Recipe calorie calculator
Compute total calories, calories per serving, and kcal per 100g from ingredient weights and kcal per 100g labels.
Tip + tax bill splitter
Split a bill with tax + tip. Even split or itemized per person, with clean rounding.
Commute cost calculator
Estimate your commute cost per day/month/year: fuel or transit + time (optional time value).
Inflation calculator
Inflation-adjust money using a simple annual rate (compound). Shareable, browser-only MVP.
Stacked discount calculator
Calculate the real final price when multiple % discounts stack, plus a coupon and tax. Shareable, browser-only.
Percent change calculator
Compute percent change (AโB), reverse a percent change, and combine two-step percentage changes. Shareable, browser-only.
Weighted average calculator
Compute a weighted average from multiple (value, weight) pairs. Useful for grades, average cost basis, and more. Shareable, browser-only.
Break-even point calculator
Compute break-even units and revenue from fixed costs, variable cost per unit, and selling price. Includes an optional target-profit goal. Shareable, browser-only.
Time block planner
Turn a task list into a time-block schedule: start time + tasks (minutes) โ blocks you can copy/share. MVP, browser-only.
Time zone difference
See what time it is in two time zones, the difference at that moment (DST-aware), and convert a specific time between zones. Shareable, browser-only.
Working days between dates
Count working days between two dates with explicit weekend rules and an optional holidays list. Choose whether to include start/end. Shareable, browser-only.
Countdown (time until a date-time)
Count down to a target date/time in a chosen time zone (DST-aware). Shows the exact target moment and a copyable summary. Shareable, browser-only.
Salary โ hourly rate converter
Convert annual salary to hourly rate (and back) using your hours/week and weeks/year. Shareable, browser-only.
Take-home pay calculator (simple)
Estimate net (take-home) pay from gross pay using a simple tax rate and deductions. Shareable, browser-only MVP.
Sleep cycle calculator
Pick a wake-up time (or bed time) and get recommended options based on a fall-asleep buffer and ~90-minute sleep cycles. Shareable, browser-only MVP.
BMI calculator
Calculate BMI and a healthy weight range from your height (metric & imperial). Shareable, browser-only.
BMI Prime calculator
Calculate BMI Prime (BMI/25) to see how your BMI compares to the common โnormalโ upper limit. Shareable, browser-only.
Running pace calculator
Convert distance + time โ pace (min/km or min/mi). Also shows speed and simple splits. Shareable, browser-only.
Ovulation window calculator
Estimate ovulation date and fertile window from last period start (LMP) and cycle length. Includes clear disclaimer. Shareable, browser-only.
Body fat calculator (US Navy method)
Estimate body fat percentage with the U.S. Navy tape-measure formula (male/female, metric & imperial). Shareable, browser-only.
Calories burned calculator (MET)
Estimate calories burned from MET ร weight ร time. Pick an activity preset or enter MET manually. Shareable, browser-only.
Calorie deficit calculator
Estimate your daily calorie deficit and target calories from TDEE and a weekly goal (kg/week or lb/week). Shareable, browser-only MVP.
Luggage size checker
Check if your bag fits common carry-on/personal-item/checked-bag size rules (max LรWรH or linear total). Shareable, browser-only MVP.
Power bank Wh โ mAh converter
Convert power bank capacity between Wh and mAh using voltage (3.7V/5V/custom). Includes common airline thresholds (100Wh/160Wh). Shareable, browser-only.
Electricity cost calculator
Estimate an electricity bill from kWh, rate per kWh, and fixed fees. Shows per-day cost with optional billing days. Shareable, browser-only MVP.
Paint calculator
Estimate how much paint you need from area, coats, and coverage (plus a waste margin). Metric + Imperial. Shareable, browser-only MVP.
Loan amortization calculator
Compute payment per period and generate an amortization schedule (monthly or weekly) with total interest. Shareable, browser-only MVP.
Compound interest calculator
Estimate future value with a fixed annual rate and regular contributions (weekly/monthly/yearly). Shareable, browser-only MVP.
Date add/subtract calculator
Add or subtract days/weeks/months/years from a date. Optional business-day mode (skip weekends + custom holidays). Shareable, browser-only MVP.
Meeting time poll (simple)
Paste time options, mark your availability (yes/maybe/no), then copy a clean summary to send to the group. Shareable, browser-only MVP.
QR code generator
Generate a QR code for text, URL, or WiโFi. Download PNG and share via a link. Browser-only MVP.
QR code generator (PNG/SVG)
Generate a QR code for text, URL, or WiโFi. Download PNG/SVG and share via a link. Browser-only MVP.
Text case converter
Convert text to UPPERCASE/lowercase/Title Case, turn identifiers into camelCase/snake_case/kebab-case, and clean whitespace. Shareable, browser-only MVP.
Recipe scaler
Scale ingredient amounts up or down by servings or multiplier. Paste one ingredient per line and get adjusted amounts. Shareable, browser-only MVP.
Water intake calculator
Estimate a daily water intake goal from weight and activity. Outputs a simple range plus cup/oz conversions. Shareable, browser-only MVP.
Mortgage affordability calculator
Estimate how much house you can afford using income, monthly debts, down payment, rate, and term. Uses simple DTI guidelines. Shareable, browser-only MVP.
Loan refinance calculator
Compare your current loan vs a refinance: payment, total interest, monthly savings, and break-even months (with fees). Shareable, browser-only MVP.
Savings rate calculator
Calculate your savings rate from income and expenses. Shows net vs gross definitions, savings amount, and a target gap. Shareable, browser-only MVP.
Emergency fund calculator
Emergency fund calculator: monthly essential expenses ร target months โ goal. See the gap and estimate months to reach it (optional interest). Shareable, browser-only MVP.
VAT calculator
Add VAT to net price, or remove VAT from gross price. Shows net, VAT amount, gross, and the multiplier. Shareable, browser-only MVP.
50/30/20 budget calculator
Split your income into needs (50%), wants (30%), and savings (20%). Enter current spending to see targets and gaps. Shareable, browser-only MVP.
Rent vs buy calculator
Compare renting vs buying a home with a simple cost model: rent growth, mortgage, taxes, maintenance, appreciation, and selling costs. Shareable, browser-only MVP.
Pomodoro timer
A simple Pomodoro timer with custom work/break lengths, optional beep, and shareable links. Browser-only MVP.
Password strength checker
Check password strength locally: estimate entropy, flag common patterns, and show rough brute-force time under different attack models. Browser-only MVP.
UUID generator
Generate UUID v4 locally in your browser. Choose format (case, hyphens, wrap), generate multiple at once, and copy/share results. Browser-only MVP.
UUID validator
Validate and normalize UUIDs (v1โv8) in your browser. Detect version/variant, accept braces/URN/no-hyphen inputs, and copy/share results. Browser-only MVP.
UUIDv7 generator
Generate UUID v7 locally in your browser (time-ordered). Batch-generate, choose format (case/hyphens/wrap), parse the embedded timestamp, and copy/share results. Browser-only MVP.
UUIDv7 parser
Parse UUID v7 locally in your browser: extract the embedded millisecond timestamp, check version/variant, and copy or share results. Browser-only MVP.
Snowflake ID decoder
Decode 64-bit Snowflake IDs locally: extract the embedded timestamp and bit fields. Includes Twitter/X and Discord presets, plus custom layouts. Copy/share results. Browser-only MVP.
ULID generator
Generate ULIDs locally in your browser (sortable IDs). Also decode a ULID to its timestamp (UTC). Copy results or share a link. Browser-only MVP.
Nano ID generator
Generate nanoid-style short IDs locally in your browser. Choose length and alphabet preset (or custom), generate in batch, then copy or share a link. Browser-only MVP.
Age calculator
Calculate age (years, months, days), total days, and days until next birthday. Shareable link. Browser-only MVP.
Packing list generator
Generate a simple travel packing checklist based on trip length, season, and trip type. Customize items, tick as you pack, and copy/share the list. Browser-only MVP.
URL encoder/decoder
Encode or decode URL strings (percent-encoding) locally. Supports encodeURIComponent vs encodeURI, optional โ+ as spaceโ decoding, and query-string parsing. Copy output or share a link. Browser-only MVP.
Regex escape
Escape plain text so it can be safely used inside a regular-expression pattern. Supports JS / Python / PCRE output formats. Copy output or share a link. Browser-only MVP.
Regex tester
Test JavaScript regular expressions (RegExp) against text locally. See matches + groups as JSON, copy results, or share a link. Browser-only MVP.
UTM builder
Build campaign URLs with UTM parameters from a base URL. Parse existing UTM links, add extra query parameters, copy the final URL or share a link. Browser-only MVP.
Meeting agenda generator
Generate a clean, time-boxed meeting agenda template from topics and total minutes. Copy output or share a link. Browser-only MVP.
Color contrast checker (WCAG)
Check WCAG contrast ratio between text and background colors. Supports HEX/RGB input, AA/AAA checks, preview, and shareable links. Browser-only MVP.
Color picker (HEX/RGB/HSL)
Convert colors between HEX/RGB/HSL. Includes a quick contrast sanity check vs black/white, copyable CSS snippet, and shareable links. Browser-only MVP.
Word counter
Count words, characters, lines, UTF-8 bytes, and estimated reading time. Optional whitespace cleanup. Copy summary or share a link. Browser-only MVP.
Slugify (text โ URL slug)
Convert text into a URL-friendly slug (kebab-case). Options for separator, lowercase, and keeping non-ASCII (Unicode) characters. Copy output or share a link. Browser-only MVP.
Text case converter
Convert text to UPPERCASE, lowercase, Title Case, Sentence case, camelCase, snake_case, and kebab-case. Copy output or share a link. Browser-only MVP.
Text line numberer
Add line numbers to text locally. Choose the start number, zero padding width, separator, and whether to ignore empty lines. Copy output or share a link. Browser-only MVP.
Text line sorter
Sort text line-by-line (AโZ / ZโA) with options to ignore case, trim whitespace, ignore empty lines, and deduplicate. Copy output or share a link. Browser-only MVP.
Text line deduper
Remove duplicate lines from text with options to ignore case, trim whitespace, and ignore empty lines. Choose to keep the original order or sort unique lines. Copy output or share a link. Browser-only MVP.
Remove duplicate lines
Remove duplicate lines with options to keep the first or keep the last occurrence (preserve order), plus ignore case, trim whitespace, and ignore empty lines. Copy output or share a link. Browser-only MVP.
Remove duplicate words
Remove duplicate words from text (dedupe words within each line). Keep the first or last occurrence (preserve order), plus ignore case and trim whitespace. Copy output or share a link. Browser-only MVP.
Text line shuffler
Shuffle text line-by-line with options to trim whitespace, ignore empty lines, and deduplicate. Add an optional seed for reproducible shuffles. Copy output or share a link. Browser-only MVP.
Markdown to HTML
Convert Markdown to HTML with a safe preview (input HTML is escaped). Copy the HTML output or share a link. Browser-only MVP.
CSS minifier / prettifier
Minify or pretty-print CSS in your browser (optional comment removal). Copy output or share a link. Browser-only MVP.
IP subnet calculator
Calculate IPv4 subnet details from IP + CIDR: network, broadcast, mask, wildcard, total/usable addresses, and usable range. Copy or share a link. Browser-only MVP.
SHA-256 hash
Compute SHA-256 hashes locally in your browser (hex or Base64). Copy output or share a link. Browser-only MVP.
HMAC
Compute HMAC-SHA256 or HMAC-SHA512 locally in your browser. Output hex/Base64, copy results, or share a link. Browser-only MVP.
Password generator
Generate strong passwords locally in your browser. Choose length and character sets, avoid ambiguous characters, copy results, or share a link. Browser-only MVP.
Unit converter
Convert length units locally in your browser (mm, cm, m, km, inch, foot, yard, mile). Copy results or share a link. Browser-only MVP.
URL parser
Parse a URL into parts (protocol/host/path/query/hash). View query params as a table or JSON. Copy results or share a link. Browser-only MVP.
Unicode inspector
Inspect text as Unicode code points (U+XXXX), UTF-16 code units, UTF-8 bytes, and normalization (NFC/NFD/NFKC/NFKD). Copy results or share a link. Browser-only MVP.
Lorem ipsum generator
Generate Lorem ipsum placeholder text by words, sentences, or paragraphs. Copy the result or share a link. Browser-only MVP.
Querystring โ JSON converter
Convert URL query strings โ JSON locally (repeated keys become arrays; supports a[]=1&a[]=2). Copy output or share a link. Browser-only MVP.
HTML escape / unescape
Escape or unescape HTML entities locally (& < > " ' โ & < > " '). Copy output or share a link. Browser-only MVP.
IBAN validator
Validate and format an IBAN locally (checksum + basic structure). Copy the formatted IBAN or share a link. Browser-only MVP.
MAC address generator
Generate random MAC addresses locally. Control separator/case and common first-byte bits (unicast, locally administered). Copy output or share a link. Browser-only MVP.
Luhn checker
Validate numbers with the Luhn algorithm (credit cards, IMEI, etc.). Also calculate the check digit. Browser-only; copy results or share a link.
Text dedent
Remove the shared leading indentation from multi-line text (dedent). Options: trim blank edges, convert tabs to spaces (configurable tab width). Copy output or share a link. Browser-only MVP.
Text trim
Trim whitespace and normalize spacing in text. Options: trim edges, trim each line, collapse extra whitespace, preserve newlines. Copy output or share a link. Browser-only MVP.
Unique lines
Remove duplicate lines from text while keeping the original order. Options: trim lines, ignore case, ignore empty lines. Copy output or share a link. Browser-only MVP.
Sort text lines
Sort lines of text (AโZ / ZโA). Options: numeric sort, ignore case, trim, ignore empty lines, unique lines. Copy output or share a link. Browser-only MVP.
Reverse text lines
Reverse the order of lines in a text block (top โ bottom). Options: trim lines, ignore empty lines. Copy output or share a link. Browser-only MVP.
Shuffle lines
Shuffle lines of text (randomize order). Options: trim lines, ignore empty lines, unique lines, seed. Copy output or share a link. Browser-only MVP.
Sample lines
Sample N lines from a block of text. Options: trim lines, ignore empty lines, with/without replacement, seed. Copy output or share a link. Browser-only MVP.
Wrap lines
Wrap each line of text to a target width. Options: trim lines, ignore empty lines, break long words. Copy output or share a link. Browser-only MVP.
Text split
Split text into a list by delimiter: newline, comma, tab, whitespace, or custom. Options: trim items, drop empty items, output as lines or JSON. Copy output or share a link. Browser-only MVP.
Text character counter
Count characters and UTF-8 bytes in text. Choose unit: JS length (UTF-16 code units), Unicode code points, or grapheme clusters. Copy the result or share a link. Browser-only MVP.
Text slugify
Turn text into a clean URL slug. Options: ASCII/unicode mode, lowercase, separator, max length. Copy the output or share a link. Browser-only MVP.
Lorem ipsum generator
Generate Lorem Ipsum placeholder text (paragraphs, sentences, or words). Optional seed for reproducible output. Copy or share a link. Browser-only MVP.
Markdown table formatter
Format a Markdown table: align columns, normalize the separator row (--- / :--- / ---: / :---:), and optionally trim cell whitespace. Copy output or share a link. Browser-only MVP.
Text table formatter
Format a plain text table by aligning columns into a fixed-width layout (spaces). Supports auto delimiter detection (tab / 2+ spaces), optional cell trim, right-align numeric columns, configurable column gap, plus copy output and share link. Browser-only MVP.
Text word counter
Count words, characters, lines, and paragraphs in text. Options: ignore empty lines; rough mode for CJK. Copy the result or share a link. Browser-only MVP.
Text join
Join multiple lines into a single line. Choose a delimiter (space/comma/tab/custom), trim each line, and ignore empty lines. Copy output or share a link. Browser-only MVP.
Text find & replace
Find and replace text locally (plain text or regex). Show match count, copy output, or share a link. Browser-only MVP.
Text wrap
Wrap text to a fixed line width locally. Keep words or hard-break. Copy output or share a link. Browser-only MVP.
Text line reverser
Reverse line order (like tac) and/or reverse characters per line. Copy output or share a link. Browser-only MVP.
JSON Lines (JSONL) viewer
Validate and view JSONL/NDJSON line by line. Shows error line numbers. Copy output or share a link. Browser-only MVP.
Remove empty lines
Remove empty lines from text. Optionally trim first and keep a single blank line between paragraphs. Copy output or share a link. Browser-only MVP.