Reduced Export Format

PGN means Portable Game Notation, a text format for recording games. The Reduced Export Format, abbreviated REF, is a specifically defined form of the PGN export format. It is intended for large collections of unannotated games and is the minimum form an exporting application must be able to generate to satisfy the specification.

A game is in REF only when all of these conditions are true:

• It contains no comments.
• Its tag section contains only the mandatory Seven Tag Roster.
• It contains no RAVs, Recursive Annotation Variations, meaning alternative lines inside parentheses.
• It contains no NAGs, Numeric Annotation Glyphs, meaning normalized assessments such as a dollar sign followed by a number.

The game retains its main moves, applicable move numbers, and final result marker. Reduced does not mean incomplete. It means optional analysis layers and supplemental descriptive data have been removed while a basic exchangeable game record remains.

Removing only visible comment text is not enough. If variations, NAGs, or extra tags remain, the file may still be valid export PGN, but it does not satisfy the REF definition.