Java Edition:Air Trade
Many methods exist that allow for the creation of villagers and wandering traders that have trades containing air, primarily through downgrading. These trades are normally unusable as no air item exists. Any trade containing air is deleted in 24w09a and beyond, but this deletion leaves gaps in the trade list that persist.
Dangers
In 1.10.2 and below, villagers that have trades with air as either the buy or sell item (not the second buy slot item) will savestate the chunk they are in. Moving these villagers becomes impossible after they are first written to disk, as they will savestate any chunk they are in instantly and vanish upon reloading if moved to a different chunk.
Attempting to hover over a buy or sell item that is air or placing emeralds into the buy slots with a trade selling air taking priority will also crash the game.
These dangers are both fixed in 16w32a (a 1.11 snapshot), which introduced the usage of a static "empty" ItemStack instance instead of using null.
Obtaining
Wrong Cake Trade
In 14w02a (a 1.8 snapshot), farmer villagers were supposed to sell cake in their tier 4 trades. However, due to a bug, farmer villagers instead sell the Cake (Block Item) for 1 emerald.[1] As the cake block does not have a registered item in 13w37a (a 1.7 snapshot) and above, opening this villager's GUI before reloading from disk after unlocking its tier 4 trades will crash the game trying to write the villager's trades to the trade packet. When the villager is saved to disk, 0 is written as the item id, converting it to air.
14w03a Item Namespace ID Downgrade
By downgrading villagers from the version range 14w03a (a 1.8 snapshot) to 1.10.2 to the version range of 12w21a (a 1.3 snapshot) to 14w02c (a 1.8 snapshot), all items inside all villager trades will be set to air. This occurs due to items being changed to use a namespace ID in 14w03a.
New Item Downgrade
Downgrading new items added to trades to versions before they existed replaces the new item with air.
| Item | Type | Profession | Pre-downgrade Range | Post-downgrade Range | Notes |
|---|---|---|---|---|---|
| Sweet Berries | Buy | Butcher (Master) | 19w11a - 24w07a | 16w32a - 18w48b | These villagers will convert to a career level 0 farmer. |
| Campfire | Sell | Fisherman (Apprentice) | 19w11a - 24w07a | 16w32a - 18w50a | Downgrading villagers to before 18w50a will convert them to a career level 0 farmer. |
| Leather Horse Armor | Sell | Leatherworker (Expert) | 19w11a - 24w07a | 16w32a - 19w07a | Downgrading villagers to before 18w50a will convert them to a career level 0 farmer. |
| Globe Banner Pattern | Sell | Cartographer (Master) | 19w11a - 24w07a | 16w32a - 19w09a | Downgrading villagers to before 18w50a will convert them to a career level 0 farmer. |
| Small Dripleaf | Sell | Wandering Trader | 21w05a - 24w07a | 19w05a - 21w03a | |
| Dripstone Block | Sell | Mason (Journeyman) | 21w13a - 24w07a | 16w32a - 20w46a | Downgrading villagers to before 18w50a will convert them to a career level 0 farmer. |
| Pointed Dripstone | Sell | Wandering Trader | 21w13a - 24w07a | 19w05a - 20w46a | |
| Rooted Dirt, Moss Block | Sell | Wandering Trader | 21w13a - 24w07a | 19w05a - 21w03a | |
| Mangrove Propagule | Sell | Wandering Trader | 22w11a - 24w07a | 19w05a - 1.18.2 | |
| Cherry Sapling | Sell | Wandering Trader | 23w07a - 24w07a | 19w05a - 23w06a |
22w13oneBlockAtATime Villagers
In the April Fools' snapshot 22w13oneBlockAtATime, villagers used a different format to store the trades list. Downgrading or upgrading a villager into 22w13oneBlockAtATime will replace all items in all trades with air.
23w13a_or_b Votes
The April Fools' snapshot 23w13a_or_b introduced several methods to obtain normally unobtainable features, this includes downgradeable items.
- The
villager_gemvote, when applied, will replace all emeralds in new villager trades with any item (without NBT), this includes downgradeable items.
The villager_gem vote will replace all emeralds of a villager's new trades with any item (without NBT). This will not replace any current trades, including items that were applied through this vote. If the vote is removed or altered, any trades created will not be altered. Villagers affected by this vote will retain their trades upon downgrading or updating. If the item does not exist within the version it is loaded in it will become air, otherwise the item will be preserved.
Item Count Downgrade
24w09a (a 1.20.5 snapshot) changed how an item's count was written to disk. Due to this change, downgrading items from the version range 24w09a to 25w42a (present) to the version range 16w32a (a 1.11 snapshot) to 24w07a (a 1.20.5 snapshot) will set their count to 0, immediately becoming an air item as the game deletes any item whose count is less than 1 in 16w32a and above. All items inside all villager trades will be set to air.
Gallery
A villager selling air for air.
A villager buying and selling a wide range of items, including air.
See also
References