We’ve been hard at work on World of Warcraft®: Warlords of Draenor™, and today we’ve entered the alpha phase of our expansion testing. As part of this, we’ll begin using public servers to host the data, which means you may begin seeing some datamined information show up in the usual places.

One of our goals for this very early stage of the Alpha is to test out some new technology in the wild with employees and friends and family, including a new file format called CASC (more on that below). As such, the expansion content available during this first phase will be quite limited—many of the expansion’s major features, such as Garrisons, won’t be available until a later point in the testing process. This early phase of testing will help us ramp up for our larger beta phase later on, when we’ll be inviting more players.

Introducing Our New File Format: CASC

For nearly 20 years, Blizzard games have used a file format called Mo’PaQ (MPQ for short) as a way to compress and store game files. We’ve been able to introduce some great new technology using MPQ, such as our streaming client, but we’ve really pushed the file format far beyond what it was ever intended to be used for. Today, it’s become the source of a number of technical limitations for World of Warcraft.

To address these limitation and help us develop new technologies that will improve everyone’s game experience for years to come, we’re introducing a new proprietary file format that we call CASC (Content Addressable Storage Container). We’ll be using this new format in the Warlords of Draenor alpha and beta tests, and our intent is to convert everyone to the new format in a pre-expansion patch.

As geeky as it may sound, we’re extremely excited to be moving to this new file format. It provides a ton of benefits not only for us and our ability to support and patch the game, but also for players. Here are just a few of the benefits of the new CASC file format:

• 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!

We’re already using this file format for Heroes of the Storm’s Technical Alpha test, and we’re looking forward to reaping its benefits for WoW. As we mentioned, the first big step in transitioning all WoW players over will be converting everyone’s World of Warcraft installs to the new file format prior to the expansion. Our goal is to make sure that’s as seamless and painless a changeover as possible, using as much of the existing installed data as possible to reduce additional downloads. We’ll have more info on the file conversion process as we get closer to the launch of Warlords of Draenor.

Signing Up for Beta

We’re still early in the Alpha testing process, but if you’re interested in opting in for a chance to participate in the Warlords of Draenor beta test later down the line, let us know you’re interested by creating a beta profile. To do so, log in to your Battle.net® account, go to Beta Profile Settings to download and run the Battle.net System Check tool, and submit (or update) your computer’s specifications. From the Beta Profile menu, make sure that Warcraft is checked, and update your beta preferences. You’re now eligible to be randomly selected for a Warlords of Draenor beta invite at a later stage of the testing process.

Account Security Reminder

As interest grows for the upcoming Warlords of Draenor expansion, please be aware of phishing attempts. Unscrupulous individuals (possibly working for the Iron Horde) may send out falsified emails purporting to be from Blizzard, but are in fact meant to steal your login credentials. For more information on how to identify these emails please refer to our Battle.net® Account Security site.

Stay tuned for more information as development and testing progresses for Warlords of Draenor™. This is just the beginning and we’ll have more information to share with you in the near future!