Fast, focused web utilities

Format and validate JSON. Indented or minified output, with clear error messages.

Encode text to Base64 or decode Base64 back to text. UTF-8 safe.

Percent-encode or decode URL components.

Decode JWT header and payload locally. Signature is not verified — paste tokens at your discretion.

Generate random UUIDs (v4) in your browser. Bulk generation up to 100 at a time.

Generate MD5, SHA-1, SHA-256, and SHA-512 hashes from text. Runs entirely in your browser.

Convert between JSON and YAML in either direction. Clear error messages with line numbers.

Check YAML syntax and surface every error with line and column. Built for k8s, GitHub Actions, and CI configs.

Test JavaScript regular expressions against text. See every match, capture groups, and flag effects in real time.

Compare two texts side by side. Line, word, or character-level diff with clear highlighting.

Encode reserved HTML characters to entities, or decode entities back. Optional escape for all non-ASCII.

Parse a URL or query string into key/value pairs, edit them, and rebuild a clean query string.

Convert between Unix timestamps and ISO 8601 dates. Local and UTC views with relative time, instant updates as you type.

Live Markdown editor with side-by-side preview. GitHub-flavored Markdown, autosave, and HTML/MD download.

Calculate IPv4 and IPv6 subnets — network, broadcast, host range, mask, and usable host count from a CIDR.

Convert between CSV and JSON, both directions. RFC 4180 parsing handles quoted fields and embedded newlines; delimiter and header options are configurable.

Searchable HTTP status code reference (1xx → 5xx) with short descriptions and typical use cases. Filter by class, copy a code, link to the IETF spec.

Validate a 5-field cron expression and preview the next N execution times, or build one from a frequency picker (minute/hour/day/week/month/year).

Format SQL queries across major dialects — PostgreSQL, MySQL, Snowflake, T-SQL, BigQuery, SQLite, and more. Keyword casing and indentation are configurable.

Validate a JSON document against a JSON Schema (Draft 2020-12 by default). Errors point to the failing path with a human-readable reason — fully client-side via Ajv.

Paste a curl command and get the equivalent fetch, axios, Go net/http, and Python requests snippet. Handles -X, -H, -d / --data, -u, --form, and multiline backslash continuation.

Drop an AWS Cost Explorer CSV export and see service / region / tag breakdowns, top spenders, month-over-month change, and a plain-language summary. Files never leave your browser.

Count characters, words, lines, and bytes — including a UTF-8 byte length for non-ASCII.

Convert text between camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE, and Title Case.

Generate placeholder text by words, sentences, or paragraphs. Choose to start with the classic "Lorem ipsum…".

Romanize Korean text using Revised Romanization (국립국어원) or McCune–Reischauer — consonant assimilation handled for common cases.

Convert Korean addresses to English form for international shipping, visas, and forms. Built-in city/province table plus auto-romanization of road and district names.

Convert Japanese addresses to English form for international shipping, visas, and forms. Type a postal code and the tool auto-fills prefecture / city / town from Japan Post data, then produces both envelope and online-form output.

Generate ASCII URL slugs from any text. Korean and Japanese kana are romanized in-place; non-ASCII symbols are stripped or transliterated. Handy for blog post URLs and filename normalization.

Convert between HEX, RGB, and HSL with an accurate live preview.

Check WCAG contrast ratios between two colors. Instant AA / AAA pass status for normal text, large text, and UI components.

Design linear and radial CSS gradients visually. Drag color stops, adjust the angle, and copy the ready-to-use background CSS.

Resize while keeping the aspect ratio — enter width or height, get the other side. Includes 16:9, 4:3, 21:9, 1:1 presets and the CSS aspect-ratio declaration.

Resize, convert (JPEG / PNG / WebP), and compress images. Files never leave your browser.

Generate a multi-size .ico file from any image — 16, 32, 48, 64, 128, 256 px embedded as PNG. Optional favicon kit with apple/android icons + manifest snippet.

Generate QR codes for text, URLs, Wi-Fi networks, and email — fully client-side, with PNG and SVG download.

Minify SVG files with SVGO — strip editor metadata, round coordinates, and shrink output while keeping rendering intact.

Inspect EXIF metadata (camera, GPS, timestamps, lens) embedded in JPEG / HEIC / TIFF files, then download a stripped copy with privacy-sensitive fields removed.

Generate a BlurHash placeholder string from any image. Compact ~30-byte hash that previews as a blurred image — perfect for image loading placeholders on Next.js, Unsplash-style feeds, and SSR.

Combine multiple PDFs into a single document. Reorder pages, then download — files never leave your browser.

Split a PDF into ranges, or extract specific pages into one file. All processing happens in your browser.

Convert each PDF page to a PNG or JPEG image. Adjustable scale, range selection, multi-page ZIP download.

Convert between metric and imperial units across length, weight, temperature, time, area, volume, speed, and data size.

Calculate compound interest with optional recurring contributions. Year-by-year breakdown table and balance growth chart.

Estimate annual paid leave entitlement by country (KR / JP / US / EU). Inputs are start date, jurisdiction, and (for JP) attendance rate.

Calculate exact age in years, months, and days. Includes Korean traditional age and next birthday countdown.

Estimate monthly take-home pay in South Korea. Subtracts the four-major social insurances (national pension, health, long-term care, employment) and the simplified income tax for 2026 brackets.

Estimate monthly take-home pay in Japan. Subtracts national income tax, resident tax, and the four-major social insurances (health, pension, employment, long-term care).

Create vector-PDF quotes, bills, and invoices for small businesses. Switch document type with one click, fill line items, and download a clean A4 PDF — Korean / Japanese / English templates with locale-aware tax (VAT 10%, 消費税 10%), currency, and business-number formats.

Browse public holidays by country and year on a clean monthly grid. 200+ countries supported.

Count business days between two dates, or add N business days to a start date. Excludes weekends and country-specific public holidays.

Convert between Korean / East Asian lunisolar calendar and Gregorian dates. Handles leap months (윤달 / 閏月) and reports the sexagenary year-cycle stem-branch.

Generate strong random passwords with adjustable length and character sets — fully client-side, with entropy and strength readout.

Generate time-based one-time passwords (RFC 6238) compatible with Google Authenticator and 1Password. Paste a base32 secret or otpauth:// URL — codes update live, fully in-browser.

Compute HMAC signatures (SHA-1, SHA-256, SHA-384, SHA-512) for a key/message pair. Output as hex or base64, fully in-browser via Web Crypto.

Generate an RSA public / private key pair in PEM format (PKCS#1 or PKCS#8). Useful for JWT signing keys, SSH testing, and one-off encryption — for production keys, use OpenSSL.

Compare the time across multiple cities at once. Slide to a meeting time and see when it lands in every other zone — DST is handled by your browser, no external lookups.

Convert between Western year and Japanese era (Meiji, Taisho, Showa, Heisei, Reiwa). Handles mid-year era transitions accurately — Heisei 1 begins 1989-01-08, Reiwa 1 begins 2019-05-01.

Classic 25 / 5 / 15 pomodoro timer with browser notifications. Tracks completed sessions across reloads via localStorage — no signup, no tracking.

Look up the Chinese zodiac animal (rat, ox, tiger, …) and the 60-year sexagenary cycle (干支) for any Western year. Shows the canonical names in Chinese, Japanese, and Korean.

Spin a roulette wheel of names or items to pick one at random. Each entry gets an equal slice; the wheel decelerates with realistic easing and shows the winner. Optional auto-remove for tournament-style elimination.

The Korean 사다리타기 / Japanese あみだくじ ladder draw. Enter N participants and N outcomes; randomly placed horizontal rungs connect each name to exactly one outcome. Click a name to trace its path.

Shuffle a list of names into balanced teams. Choose either the number of teams or the size per team; teams come out within 1 member of each other. Optional team names and one-click copy.

Shuffle a list of names into a fixed sequence — 1st, 2nd, 3rd, … Choose between instant reveal, sequential auto reveal with adjustable speed, or click-to-reveal where you pace the announcement yourself. Good for presentation order, karaoke turns, interview slots, or anything that needs a fair line-up.