Unofficial flags
Unofficial flags are either (a) flags in regular use that have no official status or (b) flag concepts that have appeared in various publications.
Examples of the former type are: Boxing kangaroo, Fighting Kiwi, Chatham Islands, Rotuma, West Irian, Jolly Roger. These are examples of flags used at sporting fixtures, reproductions of no-longer-used historical flags, or used by a regional populace out of spontaneity, though not officially approved (or gazetted).
Examples of the latter type are: North Island, South Island, Stewart Island/Rakiura, 51-Star United States Flag, Antarctica. These are examples of flag ideas put forward by vexillologists/flag designers that have been picked up by various publications (books, magazine articles, online reference sites, etc.).
Examples
    
 Chatham Islands flag (used widely, but status unofficial) Chatham Islands flag (used widely, but status unofficial)
 Unofficial local flag of Saint Pierre and Miquelon Unofficial local flag of Saint Pierre and Miquelon
 Flag of Wake Island used in military ceremonies similar to the Czech flag Flag of Wake Island used in military ceremonies similar to the Czech flag
 Korean Unification Flag, used in sports contexts Korean Unification Flag, used in sports contexts
 South Island (NZ) conceptual flag South Island (NZ) conceptual flag
 People's Flag of Milwaukee People's Flag of Milwaukee
 51-star conceptual United States flag 51-star conceptual United States flag
.svg.png.webp) Flag of Johnston Atoll (currently an uninhabited U.S. unincorporated territory) Flag of Johnston Atoll (currently an uninhabited U.S. unincorporated territory)
 
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 International Flag of Planet Earth, proposed by Oskar Pernefel International Flag of Planet Earth, proposed by Oskar Pernefel
 Red Flag used for socialist movements Red Flag used for socialist movements
.svg.png.webp) Unofficial flag of Northern Ireland, commonly used in sports Unofficial flag of Northern Ireland, commonly used in sports