diff --git a/cmd/root.go b/cmd/root.go
index 336db04..916f55b 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -66,13 +66,11 @@ func init() {
 	rootCmd.Flags().IntP("port", "p", 3000, "Port to run the server on.")
 	rootCmd.Flags().String("address", "0.0.0.0", "Address to bind the server to.")
 	rootCmd.Flags().String("secret", "", "Secret to use for the cookie.")
-	rootCmd.Flags().String("root-url", "", "Root URL of traefik.")
 	rootCmd.Flags().String("app-url", "", "The tinyauth URL.")
 	rootCmd.Flags().String("users", "", "Comma separated list of users in the format username:bcrypt-hashed-password.")
 	viper.BindEnv("port", "PORT")
 	viper.BindEnv("address", "ADDRESS")
 	viper.BindEnv("secret", "SECRET")
-	viper.BindEnv("root-url", "ROOT_URL")
 	viper.BindEnv("app-url", "APP_URL")
 	viper.BindEnv("users", "USERS")
 	viper.BindPFlags(rootCmd.Flags())
diff --git a/docker-compose.example.yml b/docker-compose.example.yml
index f6c553c..d3fc1a1 100644
--- a/docker-compose.example.yml
+++ b/docker-compose.example.yml
@@ -24,7 +24,6 @@ services:
     image: ghcr.io/steveiliop56/tinyauth:latest
     environment:
       - SECRET=some-random-32-chars-string
-      - ROOT_URL=https://example.com
       - APP_URL=https://tinyauth.example.com
       - USERS=user:$$2a$$10$$UdLYoJ5lgPsC0RKqYH/jMua7zIn0g9kPqWmhYayJYLaZQ/FTmH2/u
     labels:
diff --git a/internal/api/api.go b/internal/api/api.go
index 25a84ff..7d59472 100644
--- a/internal/api/api.go
+++ b/internal/api/api.go
@@ -11,6 +11,7 @@ import (
 	"tinyauth/internal/auth"
 	"tinyauth/internal/hooks"
 	"tinyauth/internal/types"
+	"tinyauth/internal/utils"
 
 	"github.com/gin-contrib/sessions"
 	"github.com/gin-contrib/sessions/cookie"
@@ -33,8 +34,13 @@ func Run(config types.Config, users types.UserList) {
 	fileServer := http.FileServer(http.FS(dist))
 	store := cookie.NewStore([]byte(config.Secret))
 
-	domain := strings.Split(config.RootURL, "://")[1]
+	domain, domainErr := utils.GetRootURL(config.AppURL)
 
+	if domainErr != nil {
+		log.Fatal().Err(domainErr).Msg("Failed to get domain")
+		os.Exit(1)
+	}
+	
 	store.Options(sessions.Options{
 		Domain: fmt.Sprintf(".%s", domain),
 		Path: "/",
diff --git a/internal/types/types.go b/internal/types/types.go
index dda53b3..cdefc75 100644
--- a/internal/types/types.go
+++ b/internal/types/types.go
@@ -22,7 +22,6 @@ type Config struct {
 	Port int `validate:"number" mapstructure:"port"`
 	Address string `mapstructure:"address, ip4_addr"`
 	Secret string `validate:"required,len=32" mapstructure:"secret"`
-	RootURL string `validate:"required,url" mapstructure:"root-url"`
 	AppURL string `validate:"required,url" mapstructure:"app-url"`
 	Users string `validate:"required" mapstructure:"users"`
 }
diff --git a/internal/utils/utils.go b/internal/utils/utils.go
index ecba7c8..9fc024b 100644
--- a/internal/utils/utils.go
+++ b/internal/utils/utils.go
@@ -2,6 +2,7 @@ package utils
 
 import (
 	"errors"
+	"net/url"
 	"strings"
 	"tinyauth/internal/types"
 )
@@ -26,4 +27,18 @@ func CreateUsersList(users string) (types.UserList, error) {
 	}
 
 	return userList, nil
+}
+
+func GetRootURL(urlSrc string) (string, error) {
+	urlParsed, parseErr := url.Parse(urlSrc)
+
+	if parseErr != nil {
+		return "", parseErr
+	}
+
+	urlSplitted := strings.Split(urlParsed.Host, ".")
+
+	urlFinal := urlSplitted[len(urlSplitted)-2] + "." + urlSplitted[len(urlSplitted)-1]
+
+	return urlFinal, nil
 }
\ No newline at end of file