Backpack

Backpack UI as of patch 10.0.0, with the additional four slots.

The backpack is the default bag for carrying items that every character have except for character part of the Echo Isles starting zone which it will appear after accepting  [1-10] Brace for Impact. The amount of money (, , or ) the character possesses is shown at the bottom right of the backpack window and can have up to three currencies pinned from the currency tab.

The backpack has 16 slots by default but can be expanded with 4 extra slots, for a total of 20 slots, by adding an authenticator and phone notifications to the Battle.net account. Vulpera characters have access to 8 additional slots for a total of 24 thanks to their [Alpaca Saddlebags] racial trait and a total of 28 with the authenticator and phone notification benefits.

Technical difficulties

When asked in 2011 Ask the Devs about increasing the size of the backpack or replacing it, the answer given was that it was technically challenging due to the manner in which the slot was coded and could cause major breaks in the game (such as loss of players' gear). This is because the backpack is "hard-coded" into the game, making any modification a very risky proposition. This was later expounded upon during the BlizzCon 2015 Engineering Community Amphitheater Discussion:

2015-11-07 00:00 |  Blizzard Entertainment

The original WoW developers decided that there would be an array to hold your inventory. The first several entries are things that end up on the paper doll, your head and leg slots and such. After that comes your inventory. At some point they wanted to add a bank to the game, so they added that to the end of the array. Players shouldn't be able to access their bank anywhere in the world, as it would break the code. This was handled by adding lots of statements in different places in the code, defining what the array position was where the inventory ended and where the bank begins. This value was hardcoded all over the place, but it isn't just a simple search to find them all. Some math logic may rely on it being constant. If you want to add slots to the backpack, who knows what you are going to break? It becomes very buggy and error prone, and likely that you are going to make a mistake. This mistake would break the game in a way you don't like. As a result, they would have to put amazing engineers that could be working on new features on a task to look through thousands of lines of code to find all of those cases, as well as the QA department testing every edge case in the world to ensure the change doesn't break anything. This is how we ended up with a fixed size backpack.

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This was directly contradicted the following BlizzCon 2016 during the World of Warcraft Q&A panel. According to Lead Game Designer Matt Goss, the difficulty of upgrading the backpack had been "almost a myth" that even the design team themselves had believed. The reality is that it actually isn't nearly as difficult and hopefully will be "Soon".

During BlizzCon 2017, it was announced that the number of slots could be increased by adding an authenticator to one's account. How many slots would be added was not mentioned at that time but, when the first PTR build for patch 7.3.5 became available, it would turn out to be four.

Additional notes

• By default, you can press 'Shift-B' to open and close your backpack. While 'B' opens all your bags.
• You can also close all open bag windows, including the backpack, by clicking its icon.
• You cannot move, delete, replace, or store your backpack.

Gallery

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  Original backpack icon

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  Patch 9.1.5 updated icon, used in the UI and as part of the bag slots.

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  Backpack button used as part of the bag slots with patch 10.0.0.

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  Pre-4.3.0 look, without the search bar

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  Pre-6.0.2 look, without the "Clean up Bags" button

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  Pre-10.0.0 look, with four extra bag slots unlocked since 7.3.5

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  Pre-Dragonflight Locked slots

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  Clicking the "+" sign next to the locked slots opens this popup, which will open the browser to Blizzard's account security page

Patch changes

• Patch 10.0.0 (2022-10-25): The Backpack button was changed to accommodate new UI refresh.
  
• Patch 9.1.5 (2021-11-02): Backpack icon updated.
  
• Patch 6.0.2 (2014-10-14): Added a "Clean up Bags" button to automatically sort items in the character's inventory, moving all empty slots to one area, and automatically sorting items to the correct bag. There's also the option to ignore a bag from cleanup.
  
• Patch 4.3.0 (2011-11-29): Added search bar.