diff --git a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/CreateSudokuActivity.java b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/CreateSudokuActivity.java
index b46171a..f61d2b1 100644
--- a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/CreateSudokuActivity.java
+++ b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/CreateSudokuActivity.java
@@ -195,7 +195,11 @@ public class CreateSudokuActivity extends BaseActivity implements IFinalizeDialo
             Since the GameActivity expects the links of imported sudokus to start with an url scheme,
             add one to the start of the encoded board
              */
-            intent.setData(Uri.parse(GameActivity.URL_SCHEME_WITHOUT_HOST + "://" + boardContent));
+            String scheme = GameActivity.validUris.size() > 0 ? GameActivity.validUris.get(0).getScheme()
+                    + "://" + GameActivity.validUris.get(0).getHost() : "";
+            if (!scheme.equals("") && !scheme.endsWith("/")) scheme = scheme + "/";
+
+            intent.setData(Uri.parse(scheme + boardContent));
             intent.putExtra("isCustom", true);
             startActivity(intent);
             finish();
@@ -205,23 +209,30 @@ public class CreateSudokuActivity extends BaseActivity implements IFinalizeDialo
 
     }
     public void onImportDialogPositiveClick(String input) {
-        String inputSudoku;
+        String inputSudoku = null;
+        String prefix;
+        StringBuilder errorMessage = new StringBuilder();
 
-        // a valid input needs to contain exactly one of these prefixes
-        String prefix1 = GameActivity.URL_SCHEME_WITHOUT_HOST + "://";
-        String prefix2 = GameActivity.URL_SCHEME_WITH_HOST + "://" + GameActivity.URL_HOST + "/";
+        /*  remove the present prefix, or, if the input contains none of the valid prefixes, notify the user
+         that their input is not valid */
+        for (int i = 0; i < GameActivity.validUris.size(); i++) {
+            prefix = GameActivity.validUris.get(i).getHost().equals("") ?
+                    GameActivity.validUris.get(i).getScheme() + "://" :
+                    GameActivity.validUris.get(i).getScheme() + "://" + GameActivity.validUris.get(i).getHost() + "/";
+            if (input.startsWith(prefix)) {
+                inputSudoku = input.replace(prefix, "");
+                break;
+            }
 
-        /*
-         remove the present prefix, or, if the input contains neither of the prefixes, notify the user
-         that their input is not valid
-         */
-        if (input.startsWith(prefix1)) {
-            inputSudoku = input.replace(prefix1, "");
-        } else if (input.startsWith(prefix2)) {
-            inputSudoku = input.replace(prefix2, "");
-        } else {
+            String endOfRecord = (i == GameActivity.validUris.size() - 1) ? "" : ", ";
+            errorMessage.append(prefix);
+            errorMessage.append(endOfRecord);
+        }
+
+        // the inputSudoku variable being null means the input did not match any of the valid prefixes
+        if (inputSudoku == null) {
             Toast.makeText(CreateSudokuActivity.this,
-                    this.getString(R.string.menu_import_wrong_format_custom_sudoku) + " " + prefix1 + ", " + prefix2, Toast.LENGTH_LONG).show();
+                    this.getString(R.string.menu_import_wrong_format_custom_sudoku) + " " + errorMessage.toString(), Toast.LENGTH_LONG).show();
             return;
         }
 
@@ -237,8 +248,7 @@ public class CreateSudokuActivity extends BaseActivity implements IFinalizeDialo
 
         // if the encoded sudoku is solvable, sent the code directly to the GameActivity; if not, notify the user
         if (solvable) {
-            Toast.makeText(CreateSudokuActivity.this, R.string.finished_verifying_custom_sudoku_toast, Toast.LENGTH_LONG).show();
-            int boardSize = gameController.getGameType().getSize() * gameController.getGameType().getSize();
+           int boardSize = gameController.getGameType().getSize() * gameController.getGameType().getSize();
             GameInfoContainer container = new GameInfoContainer(0, GameDifficulty.Unspecified,
                     gameController.getGameType(), new int [boardSize], new int [boardSize],
                     new boolean [boardSize][gameController.getGameType().getSize()]);
diff --git a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/GameActivity.java b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/GameActivity.java
index dc20eb6..03f86ab 100644
--- a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/GameActivity.java
+++ b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/GameActivity.java
@@ -44,6 +44,7 @@ import androidx.appcompat.app.ActionBarDrawerToggle;
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.appcompat.widget.Toolbar;
 
+import android.util.Log;
 import android.view.Gravity;
 import android.view.LayoutInflater;
 import android.view.Menu;
@@ -77,15 +78,15 @@ import org.secuso.privacyfriendlysudoku.ui.view.WinDialog;
 import org.secuso.privacyfriendlysudoku.ui.view.databinding.DialogFragmentShareBoardBinding;
 
 
+import java.util.Arrays;
 import java.util.LinkedList;
 import java.util.List;
 
 public class GameActivity extends BaseActivity implements NavigationView.OnNavigationItemSelectedListener, IGameSolvedListener ,ITimerListener, IHintDialogFragmentListener, IResetDialogFragmentListener, IShareDialogFragmentListener {
 
-    public static final String URL_SCHEME_WITHOUT_HOST = "sudoku";
-    public static final String URL_SCHEME_WITH_HOST = "http";
-    public static final String URL_SCHEME_WITH_HOST2 = "https";
-    public static final String URL_HOST = "sudoku.secuso.org";
+     public static final List<Uri> validUris = Arrays.asList(Uri.parse("sudoku://"),
+             Uri.parse("https://sudoku.secuso.org"),
+             Uri.parse("http://sudoku.secuso.org"));
 
     GameController gameController;
     SudokuFieldLayout layout;
@@ -152,7 +153,7 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
         int loadLevelID = 0;
         boolean loadLevel = false;
 
-        if(savedInstanceState == null) {
+         if(savedInstanceState == null) {
 
             Bundle extras = getIntent().getExtras();
 
@@ -174,12 +175,19 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
             if (data != null && !intentReceivedFromMainActivity) {
                 // extract encoded sudoku board from the URI
                 String input = "";
-                if (data.getScheme().equals(URL_SCHEME_WITHOUT_HOST)){
-                    input = data.getHost();
-                } else if ((data.getScheme().equals(URL_SCHEME_WITH_HOST) || data.getScheme().equals(URL_SCHEME_WITH_HOST2))
-                        && data.getHost().equals(URL_HOST)){
-                    input = data.getPath();
-                    input =input.replace("/", "");
+
+                for (int i = 0; i < validUris.size(); i++) {
+                    if (data.getScheme().equals(validUris.get(i).getScheme())) {
+                        if (validUris.get(i).getHost().equals("")) {
+                            input = data.getHost();
+                            break;
+                        }
+                        else if (data.getHost().equals(validUris.get(i).getHost())) {
+                            input = data.getPath();
+                            input =input.replace("/", "");
+                            break;
+                        }
+                    }
                 }
 
                 // Save all of the information that can be extracted from the encoded board in a GameInfoContainer object
@@ -458,8 +466,10 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
 
             case R.id.menu_share:
                 // Create import link from current sudoku board
-                String codeForClipboard = URL_SCHEME_WITHOUT_HOST + "://" + gameController.getCodeOfField();
-                String codeForClipboard1 = URL_SCHEME_WITH_HOST + "://" + URL_HOST + "/" + gameController.getCodeOfField();
+                String scheme = GameActivity.validUris.size() > 0 ? GameActivity.validUris.get(0).getScheme()
+                        + "://" + GameActivity.validUris.get(0).getHost() : "";
+                if (!scheme.equals("") && !scheme.endsWith("/")) scheme = scheme + "/";
+                String codeForClipboard = scheme + gameController.getCodeOfField();
 
                 // Create new ShareBoardDialog using the previously created links
                 ShareBoardDialog shareDialog = new ShareBoardDialog();
diff --git a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/MainActivity.java b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/MainActivity.java
index 50670a8..bb24188 100644
--- a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/MainActivity.java
+++ b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/MainActivity.java
@@ -41,7 +41,6 @@ import androidx.drawerlayout.widget.DrawerLayout;
 import androidx.appcompat.app.ActionBarDrawerToggle;
 import androidx.appcompat.widget.Toolbar;
 
-import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.MenuItem;
 import android.view.View;
@@ -434,23 +433,28 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
     }*/
 
     public void onImportDialogPositiveClick(String input) {
-        String inputSudoku;
+        String inputSudoku = null;
+        String prefix = "";
+        StringBuilder errorMessage = new StringBuilder();
 
-        // a valid input needs to contain exactly one of these prefixes
-        String prefix1 = GameActivity.URL_SCHEME_WITHOUT_HOST + "://";
-        String prefix2 = GameActivity.URL_SCHEME_WITH_HOST + "://" + GameActivity.URL_HOST + "/";
+        // a valid input needs to contain exactly one of the valid prefixes
+        for (int i = 0; i < GameActivity.validUris.size(); i++) {
+            prefix = GameActivity.validUris.get(i).getHost().equals("") ?
+                    GameActivity.validUris.get(i).getScheme() + "://" :
+                    GameActivity.validUris.get(i).getScheme() + "://" + GameActivity.validUris.get(i).getHost() + "/";
+            if (input.startsWith(prefix)) {
+                inputSudoku = input.replace(prefix, "");
+                break;
+            }
 
-        /*
-         remove the present prefix, or, if the input contains neither of the prefixes, notify the user
-         that their input is not valid
-         */
-        if (input.startsWith(prefix1)) {
-            inputSudoku = input.replace(prefix1, "");
-        } else if (input.startsWith(prefix2)) {
-            inputSudoku = input.replace(prefix2, "");
-        } else {
+            String endOfRecord = i == GameActivity.validUris.size() - 1 ? "" : ", ";
+            errorMessage.append(prefix);
+            errorMessage.append(endOfRecord);
+        }
+
+        if (inputSudoku == null) {
             Toast.makeText(MainActivity.this,
-                    this.getString(R.string.menu_import_wrong_format_custom_sudoku) + " " + prefix1 + ", " + prefix2, Toast.LENGTH_LONG).show();
+                    this.getString(R.string.menu_import_wrong_format_custom_sudoku) + " " + errorMessage.toString(), Toast.LENGTH_LONG).show();
             return;
         }
 
@@ -470,8 +474,6 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
             return;
         }
 
-        Log.i("Default_" + size + "x" + size, "SudokuTag");
-
         GameType gameType = Enum.valueOf(GameType.class, "Default_" + (int)size + "x" + (int)size);
 
         //check whether or not the sudoku is valid and has a unique solution
@@ -481,7 +483,7 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
         if (solvable) {
             Toast.makeText(MainActivity.this, R.string.finished_verifying_custom_sudoku_toast, Toast.LENGTH_LONG).show();
             final Intent intent = new Intent(this, GameActivity.class);
-            intent.setData(Uri.parse(prefix1 + inputSudoku));
+            intent.setData(Uri.parse(prefix + inputSudoku));
             startActivity(intent);
             finish();
         } else {