Use this text operation when its stated character encoding, token boundaries, normalization, case handling, and output format match the surrounding workflow.

Digits

Required string. Digits to validate.

The cited overview of Data validation supplies background for the terminology and domain context used by this tool.^[1]

Validate a sequence of digits against the Luhn checksum used by cards and account numbers. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Valid

Returned boolean. Whether the checksum passes.

Digit count

Returned integer. Number of digits after normalization.

• Unicode normalization, locale, grapheme clusters, malformed input, ambiguous syntax, and implementation-specific conventions can change text-processing results.
• Use finite inputs in the displayed units, preserve source measurements and assumptions, and independently verify consequential decisions.

Preserve the original text, test representative non-ASCII and malformed cases, and use a standards-aware parser or serializer when interoperability matters.

• GTIN Check Digit Validator

  Validate a complete GTIN-8, GTIN-12, GTIN-13, or GTIN-14, or compute the check digit from its data digits. An explicit mode avoids treating a 12- or 13-digit value as the wrong GTIN variant.

• Sudoku Grid Validator

  Check that a 9×9 Sudoku grid uses digits 0–9 and has no repeated nonzero value in any row, column, or 3×3 box. Zero represents an empty cell.

• IP Address Validator

  Validate, normalize, and classify an IPv4 or IPv6 address, including private, loopback, link-local, documentation, multicast, and globally routable ranges.