the402 x402 endpoint directory

Format a card number into the conventional display groups for its network (4-6-5 for Amex, 4-6-4 for 14-digit Diners,

Mask a card number for display, keeping the first six and last four digits (the PCI-permitted maximum) and replacing t

Detect the issuing network/brand (Visa, Mastercard, American Express, Discover, Diners Club, JCB, UnionPay, Maestro) f

Validate a payment-card number: Luhn check-digit test plus network detection and length check. A syntactically valid n

Fletcher checksum over the input payload, in 16-bit (default) or 32-bit width. Returns the checksum as an unsigned int

Adler-32 checksum (as used by zlib) over the input payload. Faster than CRC-32 but weaker for short inputs. Returns th

CRC-16 over the input payload in one of several standard variants (ccitt-false, xmodem, modbus, ibm; default ccitt-fal

CRC-32 (IEEE 802.3 polynomial, as used by zip, gzip and PNG) over the input payload. Returns the checksum as an unsign

Inspect a non-negative integer's bit structure: bit length, set-bit count (population count), trailing-zero count, pow

Circularly rotate a non-negative integer left or right within an explicit bit width (bits shifted off one end reappear

Shift a non-negative integer left or right by `amount` bits. A right shift is logical (fills with zeros). A left shift

One's-complement NOT of a non-negative integer within an explicit bit width (two's-complement domain). The value must

Bitwise XOR across two or more non-negative integers (given as decimal strings, evaluated as arbitrary-precision BigIn

Bitwise OR across two or more non-negative integers (given as decimal strings, evaluated as arbitrary-precision BigInt

Bitwise AND across two or more non-negative integers (given as decimal strings, evaluated as arbitrary-precision BigIn

Expand a fraction to its decimal form by exact long division, detecting a repeating cycle and rendering it in parenthe

Convert a decimal string to an exact reduced fraction. For a repeating decimal, set repeat to the number of trailing f

Add, subtract, multiply or divide two fractions and return the exact, fully-reduced result. All computation is done in

Reduce a fraction to lowest terms and describe it: numerator/denominator (denominator normalized positive), sign, whet

Add or subtract from a timecode, either another timecode (b) or a raw frame count (frames), at a given frame rate. Use

Rebase a timecode (or a raw frame count) from one frame rate to another on a real-time basis, so the wall-clock positi

Parse an SMPTE timecode (HH:MM:SS:FF, or HH:MM:SS;FF for drop-frame) at a given frame rate into its components, total

Split an amount into parts using integer minor-unit math so the shares always sum back to the exact original — no roun

Round an amount to a currency's minor units (or an explicit minorUnits) with a chosen rounding mode: half-even (banker

Parse a formatted money string back into a number, using the locale's grouping and decimal separators (so '1.234,56' i

Format a numeric amount as currency for a given locale using Intl, honouring the currency's own minor-unit convention

Two directions over query strings. action='parse' decodes a query string (with or without a leading '?') into an objec

Resolve a relative or absolute reference against a base URL, following RFC 3986 reference resolution (e.g. base 'https

Canonicalize a URL: WHATWG parsing already lowercases the host, resolves dot-segments and drops default ports; on top

Parse an absolute URL into its WHATWG components: protocol/scheme, credentials, host/hostname/port, origin, pathname (

Split YAML front-matter from a document — returns the parsed metadata object and the remaining content body. Malformed

Extract the heading outline from Markdown — depth, text and a unique GitHub-style anchor slug for each heading. Option

Render GitHub-Flavored Markdown to HTML. Output is sanitized by default (scripts, event handlers and javascript: URLs

Split an identifier or phrase into words and render it in every common case — camelCase, PascalCase, snake_case, kebab

Choose the singular or plural form for a given count, e.g. (apple, 3) → "apples", (apple, 1) → "apple". By default the

Return the singular form of an English word (handles irregulars — people → person, mice → mouse).

Return the plural form of an English word (handles irregulars — person → people, mouse → mice).

Spell an integer out in English words, e.g. 123 → "one hundred twenty-three". Negatives are prefixed with "minus".

Format a non-negative integer as an ordinal — both the suffixed form (21st) and the ordinal words (twenty-first).

Convert between integers (1–3999) and Roman numerals in either direction — a digit string is encoded to Roman, a Roman

Convert an integer between numeral bases 2–36 (binary, octal, hex, base36, …). Arbitrary size via BigInt; digits are c

Validate a 9-digit US ABA bank routing number by its weighted (3,7,1) mod-10 checksum. Spaces and hyphens are ignored.

Validate a 15-digit mobile device IMEI by its Luhn check digit. Spaces and hyphens are ignored.

Validate a GTIN barcode number — EAN-8, UPC-A (12), EAN-13 or GTIN-14 — by the standard mod-10 check digit. Length sel

Validate an ISBN-10 (mod-11, trailing X allowed) or ISBN-13 (GTIN mod-10) book number. Length after removing spaces/hy

Validate a number by the Luhn (mod-10) algorithm — the scheme behind credit/debit card numbers and many IDs. Spaces an

Sanitize untrusted HTML to a safe allowlist. Keeps common formatting and links but removes dangerous scripting tags, i

Return both the fully-expanded (eight 4-hex groups) and canonical compressed (RFC 5952) forms of an address. IPv4 is r

Test whether an IP address falls within a CIDR block. A well-formed address of a different family (or simply outside t

Compute network details of a CIDR block — network & broadcast address, usable host range, total and usable address cou