Because BackendTask's in elm-pages never run in the browser (see the BackendTask docs), you can access environment variables securely. As long as the environment variable isn't sent down into the final Data value, it won't end up in the client!

import BackendTask exposing (BackendTask)
import BackendTask.Env
import FatalError exposing (FatalError)


type alias EnvVariables =
    { sendGridKey : String
    , siteUrl : String
    }


sendEmail : Email -> BackendTask FatalError ()
sendEmail email =
    BackendTask.map2 EnvVariables
        (BackendTask.Env.expect "SEND_GRID_KEY" |> BackendTask.allowFatal)
        (BackendTask.Env.get "BASE_URL"
            |> BackendTask.map (Maybe.withDefault "http://localhost:1234")
        )
        |> BackendTask.andThen (sendEmailBackendTask email)


sendEmailBackendTask : Email -> EnvVariables -> BackendTask FatalError ()
sendEmailBackendTask email envVariables =
    Debug.todo "Not defined here"

Errors