• Validate normalized values against the 249 assigned ISO 3166-1 alpha-2 country codes rather than letter-count formatting alone.
• Apply the same explicit rule consistently during ingest, quality control, reporting, or preservation planning.
• Expose records that need human review without silently rewriting the source data.

Reserved, exceptional, and user-assigned pairs such as EU or XK are not the same as officially assigned ISO 3166-1 country codes.^[1]

• ISO assignments can change; applications needing live maintenance notices should refresh their code table from the ISO 3166 Maintenance Agency.
• Preserve the original value and record the rule version when using this result in an archival workflow.

• Language Code ISO 639-2 Three-Letter Validator

  Use Language Code ISO 639-2 Three-Letter Validator to validate assigned ISO 639-2 bibliographic and terminology language codes plus the qaa–qtz local-use range. Choose this tool when you need to validate normalized values against the 249 assigned ISO 3166-1 alpha-2 country codes rather than letter-count formatting alone.

• ISO 8601 Date Interval Format Validator

  Use ISO 8601 Date Interval Format Validator to validate a practical ISO 8601 start/end interval subset with real Gregorian dates, clock ranges, offsets, and durations. Choose this tool when you need to validate normalized values against the 249 assigned ISO 3166-1 alpha-2 country codes rather than letter-count formatting alone.