[MC-88967] Most NBT tags are not kept when a mob converts to another mob

The bug

When a mob transforms into another mob (ex. zombie villager → villager, mooshroom → cow), it loses most of its NBT tags. This also affects conversions to the same mob, like slimes and magma cubes splitting.
It is worth noting CustomName and NoAI are preserved (MC-6773 & MC-67437), so other tags are expected to be saved as well.

Examples

The following is a list of tags that aren't transferred between entities.

From	Husk	Zombie	Skeleton	Zombie Villager	Villager	Villager	Pig	Piglin	Piglin Brute	Hoglin	Slime	Magma Cube	Tadpole	Mooshroom
To	Zombie	Drowned	Stray	Villager	Zombie Villager	Witch	Zombified Piglin	Zombified Piglin	Zombified Piglin	Zoglin	Smaller Slime	Smaller Magame Cube	Frog	Cow
`AbsorptionAmount`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`active_effects`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`Age`, `IsBaby`	✔	✔	N/A	✔ ⁷	✔ ⁷	N/A	✔	✔	N/A	✔	N/A	N/A	N/A	❌
`AngrTime`, `Brain.memories.minecraft:angry_at.ttl`	N/A	N/A	N/A	N/A	N/A	N/A	N/A	❌	❌	N/A	N/A	N/A	N/A	N/A
`AngryAt`, `Brain.memories.minecraft:angry_at.value`	N/A	N/A	N/A	N/A	N/A	N/A	N/A	❌	❌	N/A	N/A	N/A	N/A	N/A
`ArmorItems`	✔	✔	✔	❌ ⁸	❌ ⁸	❌ ⁸	❌ ⁸	✔	✔	✔	N/A¹⁹	N/A¹⁹	❌ ⁸	❌ ⁸
`ArmorDropChances`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`Attributes`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`CanBreakDoors`	✔	❌	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
`CanPickUpLoot`	✔	✔	✔	⚠️ ⁹	❌	❌	❌	❌	❌	✔	❌	❌	❌	❌
`CustomName`	✔	✔	✔	✔	✔	✔	✔	✔	✔	✔	✔ ²⁰	✔ ²⁰	✔	✔
`CustomNameVisible`	✔	✔	✔	✔	✔	✔	✔	✔	✔	✔	❌	❌	✔	✔
`DeathLootTable`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`DeathLootTableSeed`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`FallFlying`	❌	❌	❌	❌ ⁸	❌ ⁸	❌ ⁸	❌ ⁸	❌	❌	❌	N/A¹⁹	N/A¹⁹	❌ ⁸	❌ ⁸
`Fire`	❌	❌	N/A⁵	❌	❌	❌	N/A¹⁵	N/A¹⁵	N/A¹⁵	N/A¹⁵	❌	N/A²³	❌	❌
`ForcedAge`	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	❌
`Gossips`	N/A	N/A	N/A	✔	✔	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
`HandItems`	✔	✔	✔	❌ ⁸	❌ ⁸	❌ ⁸	❌ ⁸	✔	✔	✔	N/A¹⁹	N/A¹⁹	❌ ⁸	❌ ⁸
`HandDropChances`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`Health`	❌	❌	❌	❌	N/A¹⁰	❌	❌	❌	❌	❌	N/A²¹	N/A²¹	❌	✔
`HurtByTimestamp`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`HurtTime`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌ )
`Invulnerable`	✔	✔	✔	✔	N/A¹⁰	❌	❌	❌	❌	✔	✔	✔	❌	✔
`Leash`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`LeftHanded`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`Motion`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`NoAI`	N/A⁴	N/A⁴	N/A⁶	✔	✔ ¹¹	✔ ¹³	✔ ¹³	N/A¹⁷	N/A¹⁷	N/A¹⁸	✔	✔	❌	❌
`NoGravity`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`Offers`	N/A	N/A	N/A	✔	✔	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
`OnGround`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`Passengers`¹	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	N/A	N/A	❌	❌
`PersistenceRequired`	✔	✔	❌	✔	✔	⚠️ ¹⁴	⚠️ ¹⁶	✔	✔	❌	✔	✔	⚠️ ¹⁶	✔
`PortalCooldown`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`RootVehicle`²	✔	✔	✔	✔	✔ ¹²	❌	❌	✔	✔	✔	❌	❌	❌	❌
`Rotation`³	✔	✔	✔	✔	✔	✔	✔	✔	✔	✔	❌ ²²	❌ ²²	✔	✔
`SleepingX`, `SleepingY`, `SleepingZ`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`Silent`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`Tags`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
`UUID`	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌ ²³	❌ ²³	❌	❌
`VillagerData`	N/A	N/A	N/A	✔	✔	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
`Xp`	N/A	N/A	N/A	✔	✔	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
`wasOnGround`	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	❌	❌	N/A	N/A

¹ See MC-193083.
² Not an actual tag saved on mobs, but it's the corresponding tag name on player data: the vehicle this entity rides, see also MC-193083.
³ Desynced, see MC-248587.
⁴ Cannot be converted (even when setting DrownedConversionTime with commands), see MC-148935, consider to only not trigger/count down the timer if NoAI is present, and allow value 0 to convert.
⁵ Skeletons MUST be in powdered snow to convert, even via commands. Powdered snow extinguishes burning mobs.
⁶ Cannot be converted (even when setting StrayConversionTime with commands), consider to only not trigger/count down the timer if NoAI is present, and allow value 0 to convert.
⁷ Since zombie villagers use IsBaby instead of Age, the time until growing up/being able to breed again is lost. Age gets set to 0 for adults and -24000 for babies upon converting to villagers.
⁸ The equipment is not dropped, nor brought over to the new form.
⁹ Always 1b, MC-73178.
¹⁰ Mob needs to die to convert, cannot be converted by creative players.
¹¹ MC-183860, fixed.
¹² MC-163767,fixed
¹³ MC-67437, fixed.
¹⁴ Always 1b, MC-239883, this could be resolved by making all villagers that spawned naturally be persistent instead and copying the value over.
¹⁵ Converted-to mob cannot burn, if this behavior will ever be toggle-able (for example via entity type tag), this should be synchronized though.
¹⁶ Always 1b.
¹⁷ Cannot be converted (even when setting TimeInOverworld with commands), see MC-172077, consider to only not trigger/count down the timer if NoAI is present, and allow value 0 to convert.
¹⁸ Cannot be converted (even when setting TimeInOverworld with commands), consider to only not trigger/count down the timer if NoAI is present, and allow value 0 to convert.
¹⁹ Loot is dropped due to mob death.
²⁰ MC-6773, fixed.
²¹ Mob needs to die to convert, can be converted by creative players.
²² Desynced, and randomized, see MC-248587.
²³ Mob splits into multiple mobs, so UUID cannot be preserved for all. However, 1 of the mob should be capable to get it.
²⁴ Magma cubes can't burn, if this behavior will ever be toggle-able (for example via entity type tag), this should be synchronized though.

Since zombie villagers can be converted to villagers and vise versa, the following data is problematic due to not being stored on one of the 2 parties, causing loss of data upon converting and converting back to the original form. This should probably be it's own report, but until the rest of this is fixed, it's just another "tags lost on conversion" entry.

Zombie villagers don't have ForcedAge, InLove, Inventory, LastGossipDecay, LastRestock, LoveCause, RestocksToday and Willing.
Zombie villagers don't use Brain.memories.minecraft:home, Brain.memories.minecraft:job_site, Brain.memories.minecraft:last_woken, Brain.memories.minecraft:last_worked_at_poi, Brain.memories.minecraft:meeting_point and Brain.memories.minecraft:potential_job_site.
Villagers don't have CanBreakDoors.

How to reproduce

Summon a mob with any of the above tags, and convert it.

/summon minecraft:zombie_villager ~ ~ ~ {Health:10.0f,Invulnerable:1b,Fire:100s,Tags:["foo","bar"],ConversionTime:0}

Once the mob converted, look at its NBT data
```
/data get entity @e[type=villager,limit=1,sort=nearest]
```
→ ❌ Note that the tags marked with ❌ do not persist

Linked issues

is duplicated by 45

MC-91898 If you shear the mushroom cow with tag "NoAI", normal cow will be without the tag "NoAI" Resolved

MC-97752 Converting Villager to Zombie Resolved

MC-103290 Mooshrooms face south after shearing Resolved

MC-127307 Zombies lose some properties after converting to a drowned Resolved

MC-129122 Named Zombies become despawnable after turning into drowned. Resolved

40 more links

relates to 8

MC-6773 Renaming a slime or Magma cube, Once it splits it no longer has its custom name. Resolved

MC-261666 Armor given to Villagers is lost when they convert to Zombie Villagers Resolved

MC-149679 Zombie Villagers cured into regular villagers lose numeric values on trades Open

MC-270842 Scores are not kept when a mob converts to another mob Reopened

MC-136776 Some NBT tags are not kept when fish or axolotl mobs are caught in water buckets Resolved

3 more links

Attachments

MC-88967.mp4

Comments 63

mrpingouin1 2015-09-18T01:12:16Z

Confirmed, but the title is wrong, it only apply to mobs that turn into an other one : Pigs and Villagers.

Kinda related to MC-67437.

kumasasa 2015-09-18T06:06:25Z

~~This~~ is ~~MC-67437 (reopened that)~~

qmagnet 2015-09-18T09:34:39Z

Okay but NoAI status does remain.

kumasasa 2015-09-18T22:29:37Z

Yes, I was wrong.

[Mod] redstonehelper 2015-09-21T11:49:42Z

The "villager -> zombie villager" case is covered by MC-11883.

edit: But only the profession and maybe the trades, your ticket is about tags in general.

53 more comments

marcono1234 2015-10-18T13:37:56Z

Something like this could work to "fix" this:

For all tags in the entity:
1. If the tag is also a tag of the target entity (for example Witch), use the value for the tag
2. If the tag is not a tag of the target entitiy, ignore the tag

JUE13 2017-06-25T11:28:16Z

Confirmed for 1.12 release.

violine1101 2018-03-14T21:58:34Z

Zombie → Drowned is also affected by this, see MC-127307.

tryashtar 2018-03-15T05:05:46Z

Is the set of tags that are transferred over the same between all current conversions?

bLaZe_22 2018-07-04T01:50:15Z

Can confirm for 1.13-pre5.

bLaZe_22 2018-07-05T19:12:58Z

Can confirm for 1.13-pre6.

Meri Diana 2019-01-10T22:17:46Z

Confirmed for 19w02a.

Recoded Zaphod 2019-08-17T19:57:16Z

this creates a noticeable issue in the 1.14.4 version; as players infect and cure villagers for cheaper trades, named villagers become able to despawn when in the zombie villager state despite still having their names (appearing to the player to have Persistence).

Kaley Obsidia 2019-08-31T12:22:49Z

Just watched MumboJumbo's video where his named villagers were converted to zombies and despawned. The player expectation is if you name the villager it makes the zombie villager safe, and given how much effort goes into unlocking the villagers this would be a very frustrating bug for anyone who's making villager trading setups.

Misode 2020-01-05T17:31:44Z

Affects 1.15.1

Also effects zombie -> drowned conversion, but interestingly, not their PersistenceRequired tag, which gets transferred correctly.

Misode 2020-01-09T13:42:12Z

	Drowned	Villager	Cow	Slime	Zombie Villager
`Fire`	❌	❌	❌	❌	❌
`DeathLootTable`	❌	❌	❌	❌	❌
`Tags`	❌	❌	❌	❌	❌
`Rotation`	❌	❌	❌	❌	❌
`Motion`	❌	❌	❌	❌	❌
`Silent`	❌	❌	❌	❌	❌
`Health`	❌	❌	✔	❌	❌ intended
`PersistenceRequired`	✔	✔	✔	✔	❌
`Invulnerable`	✔	✔	✔	✔	?
`CustomName`	✔	✔	✔	✔	✔

Jakob Klint 2020-01-28T06:19:26Z

I can confirm that this affects version 1.15.2. Another important nbt tag that gets lost when converting a Zombie Villager into a villager is the “CanPickUpLoot” tag.

Jakob Klint 2020-01-28T18:40:42Z

	Drowned	Villager	Cow	Slime	Zombie Villager
`Fire`	❌	❌	❌	❌	❌
`DeathLootTable`	❌	❌	❌	❌	❌
`Tags`	❌	❌	❌	❌	❌
`Rotation`	❌	❌	❌	❌	❌
`Motion`	❌	❌	❌	❌	❌
`Silent`	❌	❌	❌	❌	❌
`Health`	❌	❌	✔	❌	❌ intended
`PersistenceRequired`	✔	✔	✔	✔	❌
`Invulnerable`	✔	✔	✔	✔	?
`CustomName`	✔	✔	✔	✔	✔
CanPickUpLoot	✔	❌	-	-	❌

Gatinh0 2020-01-31T02:37:52Z

Of note, in 1.15.2 this still affects tags. Tags are lost when villager converts to zombie, and rescued back to villager.

Tags:["test_tag"]

Misode 2020-02-15T12:36:14Z

@unknown Could I have ownership of this ticket to keep it up-to-date?

violine1101 2020-02-15T15:30:14Z

According to MC-172196, PortalCooldown is affected as well.

qmagnet 2020-02-15T17:18:51Z

Yes you can have this. It's been 4 years and nothing has happened with this bug so I lost interest long ago.

Feranogame 2020-02-18T21:06:11Z

Same happens for the zombification of Piglins.

Orbic 2020-03-04T22:20:01Z

In 20w10a

Orbic 2020-03-11T21:20:55Z

In 20w11a

Orbic 2020-03-18T21:32:50Z

In 20w12a

FaRo1 2020-04-08T22:04:37Z

Apparently NoAI affects cows again (in 20w15a): https://youtu.be/-mfiua5M6qg?t=236

bugsbugsbugs 2020-04-15T10:31:56Z

I have noticed this with the direction the mob is looking. Mobs that convert into another mob don't keep the direction they are looking. This issue does not affect mobs that change the variant. For example if a mooshroom gets stuck by a lightning it keeps the direction, because it is not a seperate mob it is just a variant. Other data of the mooshroom should be also be kept.

Orbic 2020-04-29T18:01:07Z

In 20w18a

Orbic 2020-05-06T18:39:00Z

In 20w19a

Orbic 2020-06-06T23:11:41Z

In 1.16 pre-2

Orbic 2020-06-10T17:52:00Z

In 1.16 Pre 3

Iosiv Visokogorskiy 2020-06-29T23:03:56Z

Confirmed for 1.16.1

supeika 2020-07-03T16:43:45Z

you should add an image of piglins and piglin brutes transformed into zombified piglins, because that image with a zombie pigman refers to an old version, and with the 1.16 is useful having two images of that.

Avoma 2021-01-09T11:11:59Z

Can confirm in 20w51a.

Avoma 2021-01-24T11:45:17Z

Can confirm in 21w03a.

Avoma 2021-02-06T17:15:41Z

Can confirm in 21w05b.

Avoma 2021-02-12T16:18:19Z

Can confirm in 21w06a.

Avoma 2021-02-19T15:34:14Z

Can confirm in 21w07a.

Avoma 2021-02-20T17:55:49Z

I've attached an example video.

Avoma 2021-04-06T17:51:58Z

Can confirm in 21w13a.

ampolive 2021-08-21T22:12:01Z

Also affects the Attributes tag.

Avoma 2021-09-05T15:03:40Z

This ticket is actively updated by @unknown, so I don't think there is any need to transfer ownership.

user-f2760 2021-09-05T19:17:48Z

Wouldn't it just be easy to save the NBT data the mob had, and merge the data into the new mob (and apply other changes like the regeneration effect for villagers, and the dropping of equipment for drowned after that)?
(as permanent fix for this issue with all conversions)

Avoma 2021-12-08T13:10:45Z

Can confirm in 1.18.

Avoma 2022-03-10T18:50:21Z

Can confirm in 1.18.2.

Tine4k 2022-05-09T13:30:56Z

This also affects Shulker Mob Duplication, tags like the colour are kept, but things like the DeathLootTable get deleted. Can confirm this on 1.18.2 (MC-251930)

user-f2760 2022-05-09T13:33:36Z

I'd suggest reporting that separately, as it isn't a mob converting to another, but a new mob being spawned in.

user-f2760 2022-05-09T13:34:20Z

Also affects villager to witch, husk to zombie, skeleton to stray, magma cube to smaller magma cube and hoglin to zoglin.

Also for slime to smaller slime, health should be "-" as that only happens on death.

ampolive 2022-05-19T16:17:21Z

Slimes and magma cubes should also not get the bigger mob's UUID because that would result in several entities with duplicated UUIDs.

ampolive 2022-05-20T22:15:51Z

This might also affect red mooshroom / brown mooshroom conversion.

Misode 2022-05-21T00:47:58Z

This might also affect red mooshroom / brown mooshroom conversion.

That should not be the case since that conversion is done with an NBT tag rather than changing the entity ID.

ampolive 2022-05-21T01:14:58Z

Oops, I thought that they were separate entities 😛 You're right.

user-f2760 2022-07-23T15:00:22Z

Zombie villager to villager does keep rotation, it's just desynced on the client: MC-248587.

Ghoulboy 2022-08-05T13:25:47Z

Don't forget Pigs to Zombified Piglins via lightning

Avoma 2022-08-11T10:42:49Z

Can confirm in 1.19.2.

user-f2760 2023-07-12T16:02:29Z

Villager to zombie villager keeps rotation, but it is desynced; only client believes it faces south.

user-f2760 2023-08-08T11:27:59Z

Needs a HandItems/ArmorItems row, see MC-264717.

4ebugger 2023-11-21T12:36:34Z

Confirm in 1.20.2 pre1, aslo affect trial spawners.

user-f2760 2023-11-21T12:43:08Z

Spawn method has no relation to convertion.

CaptainFlame54 2024-02-16T07:57:21Z

Attrobites are also affected.

Xfrtrex 2024-06-05T01:40:04Z

Can confirm in 1.21-pre2.

Ray 2024-09-04T22:57:49Z

Villagers to witches one still does not work: ArmorItems-8 The equipment is not dropped, nor brought over to the new form.