Making happiness go up

[A cool Guy]

My current vault happiness is at 10% what am I doing wrong? Everyone has low levels except the new people who come to the vault

[malogoss]

At 10% overall, lots of room for improvement, that's the good news.

Make sure all dwellers are assigned to rooms that use their highest attribute (SPECIAL). Know that armor/clothes bonus also count for what is considered the highest attribute.

Lack of water can cause non stop irradiation. Lack of food can cause hunger/low health. Both of those will make dwellers unhappy. Make sure food and water meters stay green.

Rushing a room production and failing causes bad mood too. So rush only if necessary OR rush "for fun" and XP when the risk of incident is low. I suggest <20%.

Fix those things and 70+% happiness should happen with not much effort.

[Mardoin69]

So, if you think your vault is corrupted....then you could use a 'save editor' to try an fix it. There's a 'tools' section in them that can fix things like the infamous 'happiness bug'....etc..
This is the one I use.
https://robot9706.github.io/FSSE/

There's also one you can just use online in the web browser. Have to drag n drop your save files into the webpage. Up to you what you want to use. Just search 'Fallout Shelter Save Editor' on the web to see choices.

There are several reasons your vault happiness could go lower than 50% (default value.) To add with 'malagoss' reply, if you had dwellers die in a room and didn't remove the body (or revive them) right away....this can cause the 'doom and gloom' effect in that room--where they're afraid and depressed cuz a fellow dweller died there. This can also happen for family members of a dweller that dies in the wasteland. 'Normally,' these effects only last a somewhat short amount of time and then they start going back to normal. But, it's known to happen that the room gets permanently 'doom and gloomed' which is where the save editor 'fix' tools come in handy.

[MadameFlutterbi]

assign pets it you can too that helps, usually it is due to health or unhappy in rooms they are assigned to. Having a good weapon can help too.

[gareeth]

Other than things already covered if you have spare dwellers and don't want a baby boom they do get happier in the residence chatting with each other in same gender pairs or if you know two are too related for it you can send them in.

Although you can also pair them off and drag them apart before they go off and do the deed.

The way the game works it's easy to forget that dwellers work 24 hours a day but they do benefit from time off.

They get unhappy , understandably if a dweller dies in the room they are in so I find it helps to rotate them away . It shouldn't work but the memory of a dead dweller must be location dependent as f I don't rotate

If your vault is fairly full while a bit drastic you can always exile you saddest dwellers. That way you can have some pair of and fill their biological imperative without getting overcrowded.

[Lunar Dakrness]

sex lots of sex gets anyone up to 100% happiness

[Valhalla Awaits]

Originally posted by Lunar Dakrness:

sex lots of sex gets anyone up to 100% happiness

He ain't wrong.