diff --git a/src/main/java/minevalley/core/api/Core.java b/src/main/java/minevalley/core/api/Core.java
index db60ef3e..17703031 100644
--- a/src/main/java/minevalley/core/api/Core.java
+++ b/src/main/java/minevalley/core/api/Core.java
@@ -350,7 +350,7 @@ public static List<MetadataValue> getMetadata(Metadatable metadatable, String ke
      * @param uniqueId uniqueId to get user from
      * @return user object of the given uniqueId
      */
-    public static User getUser(String uniqueId) {
+    public static User getUser(UUID uniqueId) {
         return server.getUser(uniqueId);
     }
 
@@ -364,7 +364,7 @@ public static OnlineUser getOnlineUser(Player player) {
      * @param uniqueId unique id of the player
      * @return name of the player
      */
-    public static String getName(String uniqueId) {
+    public static String getName(UUID uniqueId) {
         return server.getName(uniqueId);
     }
 
@@ -374,7 +374,7 @@ public static String getName(String uniqueId) {
      * @param name name of the player
      * @return unique id of the player
      */
-    public static String getUniqueId(String name) {
+    public static UUID getUniqueId(String name) {
         return server.getUniqueId(name);
     }
 
diff --git a/src/main/java/minevalley/core/api/CoreServer.java b/src/main/java/minevalley/core/api/CoreServer.java
index e3bdf963..d45960e2 100644
--- a/src/main/java/minevalley/core/api/CoreServer.java
+++ b/src/main/java/minevalley/core/api/CoreServer.java
@@ -119,7 +119,7 @@ public interface CoreServer {
 
     double getStatistic(String key);
 
-    User getUser(String uuid);
+    User getUser(UUID uuid);
 
     OnlineUser getOnlineUser(Player player);
 
@@ -135,9 +135,9 @@ public interface CoreServer {
 
     Gson getGson();
 
-    String getName(String uniqueId);
+    String getName(UUID uniqueId);
 
-    String getUniqueId(String name);
+    UUID getUniqueId(String name);
 
     String removeColorCodes(String text);
 
diff --git a/src/main/java/minevalley/core/api/users/User.java b/src/main/java/minevalley/core/api/users/User.java
index 6da82aba..bf6012b5 100644
--- a/src/main/java/minevalley/core/api/users/User.java
+++ b/src/main/java/minevalley/core/api/users/User.java
@@ -12,6 +12,7 @@
 import java.time.LocalDate;
 import java.util.List;
 import java.util.Map;
+import java.util.UUID;
 
 public interface User extends Registrant {
 
@@ -24,7 +25,7 @@ public interface User extends Registrant {
      *
      * @return unique id as string
      */
-    String getUniqueId();
+    UUID getUniqueId();
 
     String getName();