@Melissa Its in settings in vercel

from your selected project click Settings>Environment Variables

Then find the var, click the 3 dots on the right

you can have 1 var for all 3 or you can have 1 for each dealers choice

or if you mean locally just make a file in the root called .env.local and use the prod value there

Vercel will also give your trouble if say you have a var 1 for prod and one for preview and you try to set the prod one for both with out deleting the preview one

Seems simple but im confused here
the branch in the preview, how to make this specific branch get the env of the production?

ok are we talking about hosted on vercel or locally

if hosted on vercel branches other then main are preview deployments

You go to your settings, you go to environment variables in vercel and you set the environment to production and preview

Then when you deploy on a branch that isn't the main or Master branch, a preview deployment will be created using the environment variables you assigned

For the new environment variables to take effect you will have to redeploy the branch

then the previews will be using production-api always unless i assign it back ! got it