diff --git a/src/main/java/org/operaton/fitpub/controller/WebFingerController.java b/src/main/java/org/operaton/fitpub/controller/WebFingerController.java
index 4083325..beec57d 100644
--- a/src/main/java/org/operaton/fitpub/controller/WebFingerController.java
+++ b/src/main/java/org/operaton/fitpub/controller/WebFingerController.java
@@ -50,8 +50,8 @@ public class WebFingerController {
             return ResponseEntity.badRequest().build();
         }
 
-        // Look up user
-        Optional<User> userOpt = userRepository.findByUsername(username);
+        // Look up user (case-insensitive)
+        Optional<User> userOpt = userRepository.findByUsernameIgnoreCase(username);
         if (userOpt.isEmpty()) {
             log.warn("User not found for WebFinger request: {}", username);
             return ResponseEntity.notFound().build();
diff --git a/src/main/java/org/operaton/fitpub/repository/UserRepository.java b/src/main/java/org/operaton/fitpub/repository/UserRepository.java
index ac0a715..cd937a3 100644
--- a/src/main/java/org/operaton/fitpub/repository/UserRepository.java
+++ b/src/main/java/org/operaton/fitpub/repository/UserRepository.java
@@ -28,6 +28,15 @@ public interface UserRepository extends JpaRepository<User, UUID> {
      */
     Optional<User> findByUsername(String username);
 
+    /**
+     * Finds a user by username (case-insensitive).
+     * Used for WebFinger discovery to allow case-insensitive lookups.
+     *
+     * @param username the username
+     * @return optional user
+     */
+    Optional<User> findByUsernameIgnoreCase(String username);
+
     /**
      * Finds a user by email.
      * Used for login and duplicate email checking.