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Encode a word with the Metaphone algorithm — more accurate than Soundex for English pronunciation.

Summarise a text's difficulty as a single consensus US grade level (averaging the five grade formulas), plus the Flesch Reading Ease, a plain-language difficulty band and an approximate age range.

Convert a decimal-degree latitude/longitude to degrees-minutes-seconds, with hemisphere letters and a formatted string for each axis.

Encode a word with the classic Soundex algorithm (letter + 3 digits) for phonetic matching of names.

Test whether an IP address falls within a CIDR block. A well-formed address of a different family (or simply outside the block) returns contains=false — not an error.

Expand an RRULE recurrence rule into its occurrence datetimes, with a human-readable description.

Estimate reading and speaking time for a text at configurable words-per-minute rates (defaults: 200 wpm reading, 130 wpm speaking).

Return the validation regular expression (source and flags) used for a country's postal codes.

Compute the WCAG 2.1 contrast ratio between two colors and whether it passes AA/AAA.

Return the synonyms of an English word, aggregated across all its senses. Optionally filter by part of speech. An unknown word returns found:false with a 200.

Validate a ULID and extract its embedded timestamp and time/random components.

Parse a note in scientific pitch notation (e.g. "A4", "C#5", "Bb3") into its letter, accidental, pitch class (0..11), octave, MIDI number and frequency in Hz (A4 = 440 Hz).

Resolve an emoji by its shortcode (e.g. "smile" or ":smile:") or exact name. Provide exactly one field. Returns the emoji, its metadata and code points.

CRC-16 over the input payload in one of several standard variants (ccitt-false, xmodem, modbus, ibm; default ccitt-false). Returns the checksum as an unsigned integer and 4-digit hex. Non-cryptographic.

Fuzzy-search emoji by name, shortcode or keyword tag, ranked exact → prefix → substring.

Validate a UUID and report its version and variant.

Bitwise OR across two or more non-negative integers (given as decimal strings, evaluated as arbitrary-precision BigInt). Returns the result in decimal, hex and binary.

Look up the definitions of an English word. Returns one entry per sense with its part of speech, definition, example sentences and synonyms. Optionally filter by part of speech. An unknown word returns found:false with a 200.

Add an ISO 8601 duration to a start date or date-time and return the resulting UTC instant. Calendar-aware: months and years honor month lengths (e.g. Jan 31 + P1M clamps to the last day of February). A negative-signed duration subtracts.

Convert decimal lat/lon to a UTM coordinate (zone, latitude band, hemisphere, easting, northing) on WGS84, including the Norway/Svalbard zone exceptions. Defined for latitudes -80..84.

Canonicalize a URL: WHATWG parsing already lowercases the host, resolves dot-segments and drops default ports; on top of that, query parameters are sorted by default and you can optionally drop the fragment or a trailing slash. Returns the normalized URL and whether it changed.

Fletcher checksum over the input payload, in 16-bit (default) or 32-bit width. Returns the checksum as an unsigned integer and hex. Non-cryptographic.

Parse any CSS color and return it as hex, rgb, hsl, hwb, lab, lch and oklch.

Convert text into a URL-safe slug: transliterate accents, apply a locale character map, and join with a separator.