which folder to be deployed out folder or .next folder?

if didn't add the output key in next.config.ts then you will deploy .next folder

if you added output:'export' in next config, then you deploy the out folder

i have removed output:'export'

i am not using output:'export' for static pages

yeah then you need to deploy .next

working on it

is there any documentation for this ?

.next doesnot have index.html and without index.html firebase is not deploying

.next folder is when you deploy to something like vercel where you use full features of nextjs. To get the index.html to deploy on firebase, you need to set the output to export in next config and it will create out folder but then few features won't work