This wiki contains inaccurate and out-of-date information. Please head over to for more accurate and up-to-date game information.



Blizzard Downloader (or Blizzard Background Downloader, Background Downloader, BackgroundDownloader.exe, and others named something-BKGND-downloader) is a combination BitTorrent/HTTP client used for Blizzard Entertainment's software products. It was first implemented with the MMORPG World of Warcraft. It is used to download the full game installer package, and periodic updates for the game. It is also used to download the trailers for The Burning Crusade, StarCraft II, and Diablo III. Early versions were based on the source code of the original BitTorrent client, though it is unclear what the source model is now. When a large update is issued, Blizzard Downloader is downloaded to the WoW directory and it fetches the update file, using TCP ports 3724 and 6881. Blizzard offers an individual client for each download they offer, instead of just a torrent file. Blizzard Downloader also runs in the background under the name of Background Downloader. While the downloader is running, the program also uploads parts of files over the internet to other users who need the same data. To pause a download in progress, simply close the downloader program (do not cancel the download first) and it should resume where it left off when you start the downloader again.

New Cataclysm look

World of Warcraft: Cataclysm This section concerns content exclusive to Cataclysm.

The new look as of patch 4.3.4.

Sometime during the World of Warcraft: Cataclysm Cataclysm expansion, the downloader's look was updated to match the overall look of the expansion. Because the downloader is rarely seen standalone, most players won't notice it's new look. The downloader is now usually only called from the launcher, if set to run while the main game is running.

New Wrath of the Lich King look

World of Warcraft: Wrath of the Lich King This section concerns content exclusive to Wrath of the Lich King.

The new look as of patch 3.0.8.

Updated look with patch 3.2.

In patch 3.0.8, the look of the downloader was upgraded to match the launcher and made to look more specific to World of Warcraft. Previously, the window was much simpler with considerably less artistry. There were no obvious functional improvements, but the splash art could possibly change with each patch or for different product downloads (assuming it is still used for non- World of Warcraft products).

The downloader was further changed with patch 3.2.

The broken Background Downloader

World of Warcraft: Wrath of the Lich King This section concerns content exclusive to Wrath of the Lich King.

Blizzard Downloader 3 0 8 No Patch.jpg

On Windows PCs circa the World of Warcraft: Wrath of the Lich King Wrath of the Lich King expansion, many people had found out their Background Downloader would not execute and popup after WoW had been closed. This would prevent people from pre-downloading patches. The problem was fixed by deleting the file BackgroundDownloader.exe and running the repair program to download a new one.

Known Broken Downloaders

  • 3.3.2 to 3.3.3
  • 3.3.3 to 4.0.1

To Fix

  • Delete the BackgroundDownloader.exe in your WoW directory. In Windows its usually "C:\Program Files\World of Warcraft".
  • Run the "Repair" program and it will download a new background downloader.
  • Either run WoW and the close the game to launch it, or manually execute it from the WoW directory.


The Blizzard Downloader bundle is actually a plain BitTorrent client that has at least one .torrent file inside. The .torrent can be opened by other BitTorrent clients giving the user greater control over how the download is handled.

It is possible to extract the .torrent file from the end of the downloader executable:

Windows version

  • Search for d8:announce at the end of the downloader executable, and then save from this point to the end of the executable to a separate file. Add .torrent to the file name and open in any BitTorrent client.
  • Note that these executables may contain multiple torrent files (e.g. the Burning Crusade Downloader contains a "slim" torrent for 1.24 GB and a "full" torrent for 2.23 GB).

Earlier versions included a Macintosh-variant of the .torrent as well, but this has been removed in later versions. You may also need to remove some trailing characters at the end of the file, since they do not all belong to the .torrent; essentially, the resulting file has to be Bencode-compliant.

Alternatively, start the background downloader and check the end of Logs\BackgroundDownload.log for a message like this:

  • Creating cache file C:\Program Files\World of Warcraft\Cache\BackgroundDownload.torrent

This .torrent file can be used with any BitTorrent client. Alternate locations may include the Cache folder, depending on the WoW client's locality.

Macintosh version

  • /Applications/World of Warcraft/
    • MacOS/
      • Blizzard Downloader - executable file
    • Resources/
      • downloader.torrent - torrent file
Note: GUI & localization files not listed for readability.


Mac version

  • Background 3.0.0 - Released 13-Apr-2012 on Live (WoW version
    • - Released 13-Apr-2012 on Live (WoW version
  • Background 3.0.0 - Released 9-Oct-2011 on PTR (WoW version and 9-Nov-2011 on Live (WoW version
    • - Released 11-Nov-2011 on Live (WoW version
  • Background 2.2.1 (1498) - Released 26-Apr-2011 (WoW version
  • Background 2.2.1 - Released 26-Jan-2011 (WoW version
  • 2.2.0 - Released 8-Dec-2010

Windows version

  • BackgroundDownloader.exe - As of Patch 4.3.3 build 15354 on 3-Apr-2012.
  • ...


See also

External links

BitTorrent info

Icon-wikipedia-22x22.png Comparison of BitTorrent software on Wikipedia.

World of Warcraft: Mists of Pandaria β News