EAN-13 Validator

Purpose & User Intent: The tool validates EAN-13 codes for data quality in product catalogs, ERP feeds, and inventory systems. Target users include data engineers, catalog managers, and QA teams who process barcode data during ingestion or cataloging. It targets early error detection, GS1-consistent formatting, and reliable downstream processing.
Core Logic & Features: Implements input normalization, length enforcement (13 digits), numeric validation, and modulo-10 checksum verification. Required features: strict 13-digit input, digits-only content, and correct checksum. Optional/advanced features: accept separators, report detailed failure reasons, and provide a machine-readable result suitable for pipelines.
Inputs & Outputs: Accepts a single string input; normalization strips spaces or dashes and yields a 13-digit value. Outputs include validity boolean, calculated checksum digit, normalized code, and a structured validation breakdown for auditing.
Algorithms & Calculations: Checksum uses weights 1 and 3 on the first 12 digits; sum = Σ (digit(i) × (3 if i is odd else 1)); checksum = (10 − (sum mod 10)) mod 10.
Error & Edge Cases: Handles inputs with incorrect length, non-numeric characters after normalization, leading zeros, and checksum mismatches; returns explicit reasons such as length error or invalid checksum.
Industry/Region & Localization: Aligns with GS1/EAN-13 standards; tolerant of common separators; locale-agnostic beyond formatting hints for en-us.
Assumptions & Exclusions: Assumes a single EAN-13 input; does not validate manufacturer data or cross-check against external GS1 databases; excludes EAN-13-2, EAN-8, or non-GS1 formats.