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Tags are text slugs stored in the Tags Article of the "M" namespace of a ZIM file.

A ZIM file can have zero, one or many Tags. Should there be more than one, those are separated by the ; character.


Tags are used by publishers to classify ZIM files.

Setting Tags

Tags should help represent, classify or identify a ZIM. ZIM readers are responsible for making use of Tags or not.

Tags are commonly displayed to reader users at ZIM-selection stage and not when using a ZIM file.

Tags are free text and can thus contain any UTF-8 character except for the ; separator. It is common to restrict Tags to single or two-words combination. Concision is important for users to remember and identify content.

Private Tags

Any Tag starting with the _ (underscore) character is considered a private tag. Private tagging is a convention and nor par of the specification.

Private tags are usually hidden by readers and used as flexible metadata.

Common private tags used by kiwix Publishers:

  • _sw:<no|yes>: indicates wheter the ZIM file relies on Service Workers.
  • _ftindex:<no|yes>: indicates wheter the ZIM file includes a full-text index.
  • _pictures:<no|yes>: indicates whether the ZIM file includes pictures.
  • _videos:<no|yes>: indicates whether the ZIM file includes videos.
  • _details:<no|yes>: indicates whether the ZIM file includes detailed content.
  • _category:<xxx>: indicates that the ZIM file could be categorized as xxx. ZIM readers don't have to follow this convention. Kiwix readers don't even use the _category Tag in readers but uses it to inform its separate filtering mechanism.