How does the Blizzard Downloader work?
The Blizzard Downloader allows users to download large files using a peer-to-peer protocol.

Each person downloading the file will offer a portion of their upload bandwidth to allow other users to download the same file. By using the upload bandwidth only, the individual user will not see a decrease in their download speed - in fact, the more users there are downloading the file, the faster everyone's individual download speed will be.

The Blizzard Downloader is only active when you are downloading files, and only accesses files associated with the data that you are downloading. Blizzard will not access or upload any other files, or obtain any personal information about you as a result of this activity.

Why isn't Blizzard supplying its own bandwidth to distribute patches and other content?
As in the past, Blizzard provides a large amount of its own bandwidth for distributing content. Peer-to-peer bandwidth is added on top of that to make the download faster for everyone.

Why isn't Blizzard buying more bandwidth to distribute content by itself?
Due to the incredible popularity of our games, buying enough bandwidth to deliver large amounts of content to our users as fast as they can download it is simply not an option. It is not feasible to get that amount of bandwidth at our datacenters. Peer-to-peer transfer of files scales much better when distributing large amounts of data to a large population of users in a timely manner.

What if I can't or don't want to use a peer to peer download?
If you would like to use the built-in alternate download method, you can un-check the box for peer-to-peer downloading. This will reduce the potential download speed, since it is not as fast as peer-to-peer, but will draw the patch file directly from Blizzard's servers.

What files are being shared by the Blizzard Downloader?
The only files that are shared are the ones that the downloader is currently downloading. The downloader does not allow other peers to access arbitrary files on your computer. Files are only shared while the downloader is running.

Can I resume an incomplete download with the Blizzard Downloader?
Yes, when restarting the downloader, you can resume your existing download if you save to the same location.

Why would I want to use the Blizzard Downloader?
If you have ever downloaded a large file from the internet, you know it can be time consuming and is often limited by the host's available bandwidth. By using the Blizzard Downloader, the user is not limited by any one host's capabilities - instead, the files are distributed across a wide range of users, allowing for a quicker download for everyone. By using the upload capabilities of each downloader, the overall file distribution is much more efficient for everyone.

Another benefit of using the Blizzard Downloader is that unlike a standard website download, it checks each segment of the file download to make sure that its size is correct. This built-in error checking can prevent download corruptions commonly associated with standard FTP downloads.

Can I receive corrupt data from other people downloading?
Every piece of data received from other users is verified before being written to the disk, so it is impossible for you to accept bad data from other users.

I have played other online games, and they all offer a direct download for patches. Why does this game require use of the Blizzard Downloader?
Due to the size of our updates, the Blizzard Downloader is the fastest way to distribute patches and content to our users. If we did not use the Downloader, users would experience long download queues and/or slower download rates. The Blizzard Downloader distributes patches faster than the method used in all of our previous games.

The 'Estimated Download Time' is displaying "Calculating." How long is the download going to take?
The 'Estimated Download Time' field will not be displayed until you have connected to an optimal number of peers and your connection speed has reached optimum levels. This is to prevent inaccurate estimates from causing confusion. When the Downloader switches peers, this may revert to "Calculating" but it should eventually return to a normal estimate.

I'm constantly displaying a "connecting to peers" message.
If you are using a firewall, ports 6112, 3724, and 6881 through 6999 must be open in order for the Blizzard Downloader to connect correctly. If you are using a router, you may also need to set up port forwarding for these ports. Refer to your firewall/router's documentation for instructions on opening ports and setting up port forwarding.

For more information regarding this error, please check out our "Blizzard Downloader Fails to Connect to Tracker or Peers" page, found at this link:
http://eu.blizzard.com/support/article.xml?articleId=19616

For detailed assistance with configuring common routers for the Blizzard Downloader, visit this page:
http://eu.blizzard.com/support/article.xml?articleId=19445

I'm getting a slow download speed, what can I do to improve it?
If you are using a firewall or router, be sure that ports 6112, 3724, and 6881 through 6999 are open and forwarded to your computer and only your computer. Refer to your firewall/router's documentation for instructions on opening ports and setting up port forwarding. Also, make sure that no other programs that use bandwidth are running while using the Blizzard Downloader.

Please consult our Slow Download Speeds page for more information:
http://eu.blizzard.com/support/article.xml?articleId=19615

For more assistance with setting up your router or firewall, or for other assistance with the Blizzard Downloader, see this page:
http://us.blizzard.com/support/index.xml?categoryId=2326&rootCategoryId=2316&gameId=11

I go to college and my network administrator blocked the ports required by the Blizzard Downloader. What can I do?
After a few minutes, the downloader will adjust to users behind network firewalls and begin to download the file through an alternative transfer method. This method will be slower than if the ports were open.

I am a network administrator for a campus or company. We would like to offer our users the ability to operate the Blizzard Downloader. How do we obtain the necessary information?
If you are an administrator for a network, please contact us directly at wowtech@blizzard.com for configuration information on how to allow access to the Blizzard Downloader.

General networking assistance for the Blizzard Download can also be found online at this page:
http://us.blizzard.com/support/article.xml?articleId=21077

The downloader is crashing/freezing or giving me an error message. What do I do?
Many customers report that issues such as these can be remedied by updating their network card drivers. Please take a look at our Blizzard Downloader support page for information on some common errors and their solutions: http://us.blizzard.com/support/index.xml?categoryId=2326&rootCategoryId=2316&gameId=11

We have a Technical Support Forum available online for users who are having unusual errors while using the Blizzard Downloader. We strongly recommend that you post as much information as possible about the problem there, so that our support team can investigate your error and help resolve the issue as quickly as possible.

World of Warcraft Technical Support Forum:
http://forums.worldofwarcraft.com/board.html?forumId=11110

You can also contact our Technical Support department directly:
http://www.worldofwarcraft.com/support/