The tag consists of the keyword tag followed by a nonempty quoted string, the name.
    tag "White"
    tag "CustomTag"

The value of the tag filter is the value of the tag named name in the PGN header. If no such tag exists, th tag filter fails to match. The name is case-sensitive.

CQL currently does not support "FEN", "Round", "Result" as allowed tag names to query with tag. In addition, tag does not support any tag name beginning with the strings "White" or "Black", other than those exact strings.


The tag filter can be used to get a higher-precision date sort among those databases that support the UTCDate tag:
    sort "UTC Date" tag "UTCDate"
The tag filter is also useful for accessing custom tags created with settag :
    X=tag "CustomTag"