Changes

Since its creation in the 1980s, ''Warhammer 40,000'' has had eight ten distinct versions or editions. With each edition, the Codex of each army has changed to reflect the new rules and units.

Usually one codex is valid until a revision is made, so all codexes from the 6th, 5th, 4th and 3rd Editions of ''Warhammer 40,000'' are still valid in the current, 9th Edition, unless a later version has replaced it. There have been instances of codices that are not "standalone". They were known as "mini-dexes"or Codex Supplements. These were usually army lists that were variants of a mainstream army. An example would be the early 3rd Edition ''Codex: Catachans'', which required the main ''Codex: Imperial Guard'' to use. Mini-dexes are more or less extinct nowadays.