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Convert decimal lat/lon to a Military Grid Reference System (MGRS) string on WGS84. Precision is the number of digits per axis (1–5; 5 = 1-metre resolution, default 5).

Convert an ISO datetime into another timezone, with offset, weekday and Unix time.

Build the flag emoji for an ISO 3166-1 alpha-2 country code from its regional-indicator symbols (e.g. "US" → 🇺🇸). Non two-letter codes are clean 400s.

Normalise a postal code's casing and whitespace (uppercase, collapse runs of spaces) and report whether the normalised form is valid for the country.

Generate one or more lexicographically sortable ULIDs (monotonic within a call).

Map a WGS84 coordinate at a given zoom (0..30) to its slippy-map (XYZ / Google / OSM) tile x,y and its Bing quadkey.

Encode a coordinate to a geohash and return its bounding box and 8 neighbors.

Un-project Web Mercator (EPSG:3857) easting/northing in metres back to WGS84 longitude/latitude in degrees.

Generate a random string of a given length from a named charset (alphanumeric, alpha, lower, upper, numeric, hex, base58) or a custom alphabet. Unbiased character selection.

Derive the modified EUI-64 interface identifier from a 48-bit MAC (insert FFFE, flip the U/L bit) and the resulting IPv6 link-local address (fe80::/64).

Guess the character set of a base64-encoded byte buffer: sniffs a byte-order mark, then falls back to ASCII / UTF-8 validation and a UTF-16 NUL-pattern heuristic. Returns a best-effort charset with a confidence label — a low-confidence guess is still a successful 200.

Encode a word with Double Metaphone, returning a primary and a secondary code to capture alternate pronunciations (useful for non-English names).

Encode text to HTML entities so it can be safely embedded in markup. By default uses hex numeric references; set useNamedReferences for named entities (&, ©) or encodeEverything to encode every character.

Spell text using the NATO/ICAO phonetic alphabet (A→Alfa, B→Bravo, …), including digits and spaces (→Space). Characters with no phonetic spelling are clean 400s.

Look up an airport by its 3-letter IATA code or 4-character ICAO code. Provide exactly one. Returns the airport name, both codes, city, country, coordinates, elevation and type.

Choose the singular or plural form for a given count, e.g. (apple, 3) → "apples", (apple, 1) → "apple". By default the count is prepended ("3 apples"); set includeCount=false to omit it.

Convert an MGRS grid reference back to decimal lat/lon on WGS84 (the coordinate of the grid cell's south-west corner at the given precision). Whitespace is ignored; a malformed reference is a clean 400.

Resolve a single code point (given as 'char' or 'codepoint') to its name, general category, block, script and plane. Provide exactly one of the two inputs.

Recase a string into camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE, dot.case, path/case, Sentence case, Capital Case, Train-Case, no case, Title Case, or plain UPPER/lower — the word boundaries are detected regardless of the input casing.

Check whether a postal / ZIP code is well-formed for a country (ISO 3166-1 alpha-2). A malformed code is a successful result with `valid:false`, not an error — only an unsupported country or empty code is a 400.

Parse an absolute URL into its WHATWG components: protocol/scheme, credentials, host/hostname/port, origin, pathname (plus path segments), search (plus a decoded query object) and hash. A string that is not a valid absolute URL is rejected as a clean 400.

Build a valid .ics document from event fields (summary, start/end, location, …).

Parse an IPv4 or IPv6 address and classify it — version, normalized form and RFC range (unicast, private, loopback, linkLocal, multicast, uniqueLocal, ipv4Mapped, …). Detects IPv4-mapped IPv6.

Decode international Morse code back into text. Letters are separated by whitespace and words by "/". Unknown Morse sequences are clean 400s.