Summary

  • An applied-for IDN U-label must contain at least two Unicode code points with General Category L.
  • Code points with General Category M do not count when ICANN determines whether the IDN is a single character.

The 2026 Applicant Guidebook requires an applied-for IDN in U-label format to be longer than a single character. It defines that floor precisely: the U-label must contain at least two code points whose Unicode General Category value is L.

The Guidebook expressly excludes code points with General Category M when determining whether an applied-for IDN is a single character. Adding a combining mark to one qualifying letter therefore does not supply the required second category-L code point.

This rule sits inside a wider technical gate. The proposed IDN must comply with IDNA2008 and all standards-track RFCs that update it as well as the applicable RZ-LGR. Meeting the letter-count floor alone does not prove full conformance.

The checks are operational, not advisory. DNS Stability verifications run automatically when the applicant enters the string. A failed verification returns an error and prevents the application from proceeding; a non-conforming string deemed invalid or blocked by the RZ-LGR algorithmic check is not accepted by the submission system.

BTW recommends preserving the exact U-label under review and recording separate counts for General Category L and M before filing. This is editorial guidance, not an ICANN requirement.

Sources