Content Addressable Storage Container

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Content Addressable Storage Container (abbreviated as CASC) is a file format that works the same as MPQ but provides more benefits. This file format was first found being used for the Heroes of the Storm technical alpha but later introduced during the Warlords of Draenor alpha test.[1] It replaced the MPQ files entirely when patch 6.0.2 was released. Later February 2015, Diablo III patch 2.2.0 was announced to move to the new file format.[2] StarCraft II finally moved to this new storage on patch 3.0.0, released on October 6, 2015.[3]

Supported games

These are the following games and applications that use this new file format, in chronological order:

  1. Heroes of the Storm, beginning of development
  2. World of Warcraft, patch 6.0.2
  3. Diablo III, patch 2.2.0
  4. StarCraft II, build 38996, Legacy of the Void
  5. Overwatch, build 24919
  6. Hearthstone, sometime after The Grand Tournament
  7. StarCraft: Remastered, build 2457
  8. Warcraft III, patch 1.30.0, build 9655 PTR
  9. Call of Duty: Black Ops 4, developed by Treyarch
  10. Call of Duty: Modern Warfare, developed by Infinity Ward


  • File Corruption — File repair tools are a thing of the past. The file structure maintains itself, helping to prevent errors during installation.
  • Speed — Real-world game performance should increase for many players thanks to a non-redundant file structure—in layman’s terms, the game can find the assets it’s looking for more quickly.
  • Patching — Updating your game files should be faster and more reliable. Patch data is integrated seamlessly, and no longer requires double the installation size on-disk when patching.
  • Client Hotfixing — CASC allows us to be able to hotfix client game data, similar to server hotfixes, giving us the ability to address client-side issues that would normally require a patch.
  • Streaming — The new format provides better support for streaming data and gives us greater flexibility to define how content updates are delivered and released.
  • Expandable — The file structure is built to allow easy integration of new technologies in the future that we haven’t even thought up yet.
  • ... and more!


  1. ^ Blizzard Entertainment 2014-04-03. Warlords of Draenor™ Alpha Testing Begins. Blizzard Entertainment. Archived from the original on 2014-04-03.
  2. ^ Tyvalir 2015-02-19. First Look: Patch 2.2.0. Blizzard Entertainment. Archived from the original on 2015-03-07.
  3. ^ Blizzard Entertainment 2015-10-06. Heart of the Swarm 3.0 Patch Notes. Blizzard Entertainment. Archived from the original on 2015-10-10.

External links