The tags resource system a central and distinguishing feature of Halo's engine, dating back even to Myth. While the core mechanics are implemented in the game's code, nearly everything else is data-driven using tags. They are used across all Halo games and represent all assets and entities in the game world, such as textures, models, particle effects, AI behaviours, and weapons.

Halo's engine is itself a sort of sandbox providing the basis of a first-person shooter with systems like physics, AI, and scripting. Within this framework, tags are what allowed Bungie's artists (and now you) to create a huge variety of assets, objects, effects, and experiences without having to code.

Tags are packaged into distributable maps.

Creating and editing tags

Each games' mod tools ship with a set of stock tags needed to build the game's original maps, as well as a set of tools used to create and edit tags. Your workflows might include:

• Creating a new texture by compiling a TIFF to bitmap tag format using Tool.
• Changing the type of projectile a weapon fires by editing its tag in Guerilla.
• Placing new AI encounters in a scenario using Sapien.

Tag groups

Tags come in many different types (called tag classes or groups), each with a predefined structure and data fields, and they may depend on other tags by reference. The set of tag groups is different in each game, and tags are not transferrable between games because their structure has changed.

Tags vs. maps

A map cache file is basically just a way to package the tags needed for a level into a file that can be efficiently loaded by the release build of the game. Tags are still the core resources. Some builds of Halo's engine, such as the Standalone and Sapien tools, directly load loose tags files from the mod tools tags folder rather than map files. This is slower but allows for quicker iteration during development of mods.

Modders should consider tags to be an output of their modding efforts, not just maps. The games and their stock tags still receive updates so it may be necessary to generate new versions of your mod's map files, and this is easy to do if you maintain your tags. 343 industries avoids breaking backwards compatibility with tags, but changes to the map format may be necessary to improve the engine or add new capabilities.