checkdigit.openverbs.com/v1/luhn

Validate a number by the Luhn (mod-10) algorithm — the scheme behind credit/debit card numbers and many IDs. Spaces and hyphens are ignored. A mismatched check digit is a successful { valid: false }.

Price $0.002
Method GET
Protocol x402
Last probe 402
Verified 2026-10-01

Call it

# 1. Ask the endpoint what it costs (no payment, no wallet needed):
curl -i -X GET 'https://checkdigit.openverbs.com/v1/luhn'

# -> HTTP/1.1 402 Payment Required
#    the response carries the price, asset and pay-to address.

# 2. Pay and retry with any x402 client:
npx x402-fetch 'https://checkdigit.openverbs.com/v1/luhn'

Endpoint: https://checkdigit.openverbs.com/v1/luhn. Operated by checkdigit.openverbs.com, not by Animica. Price and availability were correct at the last probe on 2026-10-01 and are set by the operator, who may change them.

Other endpoints on checkdigit.openverbs.com

checkdigit.openverbs.com/v1/ean

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

GET · $0.002

checkdigit.openverbs.com/v1/isbn

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

GET · $0.002

All 3 endpoints on checkdigit.openverbs.com →